Optical switch devices

ABSTRACT

A security device includes an array of lenses and a plurality of first and second segments disposed under the array of lenses. At a first viewing angle, the array of lenses presents a first image for viewing without presenting the second image for viewing, and at a second viewing angle different from the first viewing angle, the array of lenses presents for viewing the second image without presenting the first image for viewing. At least one first or second segment can include one or more microstructures or one or more nanostructures configured to produce one or more colors for the first or second image.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/326,707, entitled “OPTICAL SWITCH DEVICES,” filedApr. 22, 2016, to U.S. Provisional Application No. 62/446,315, entitled“OPTICAL SWITCH DEVICES,” filed Jan. 13, 2017, and to U.S. ProvisionalApplication No. 62/447,842, entitled “OPTICAL SWITCH DEVICES,” filedJan. 18, 2017. The entirety of each application referenced in thisparagraph is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED R&D

This invention was made with government support under Contract No. TEPS14-02302 awarded by the Bureau of Engraving and Printing. The governmenthas certain rights in the invention.

TECHNICAL FIELD

The present application generally relates to optical switch devices. Inparticular, the optical switch devices include optical features and/orcolor generating structures (e.g., microstructures and/or nanostructuresconfigured to provide one or more colors) under an array of lenses topresent an icon for viewing when illuminated.

DESCRIPTION OF THE RELATED TECHNOLOGY

Optical switch devices can be used as a security device, such as ananti-counterfeit feature (for example, on a banknote). Holograms havebeen used as a counterfeit deterrent. However, this technology hasbecome so widespread with hundreds if not thousands of holographic shopsaround the world that holograms are now viewed by some as having poorsecurity. Optically variable inks and optically variable magnetic inkshave also been used on banknotes. However, these products have now beensimulated or have been even made from similar materials as the originalsthat these security elements are now questionable as a high securityfeature. Motion type security elements have been adopted into banknotes,but even here, this feature has also been used widely on commercialproducts. Thus, with respect to security devices, a new security featurethat is difficult to counterfeit and can be readily incorporated into anitem such as a banknote is desirable.

SUMMARY

In accordance with certain embodiments described herein, optical switchdevices, such as security devices are disclosed. Advantageously, thesecurity devices disclosed herein can present sharp, high contrastimages with or without color that switch rapidly, which are difficult tocounterfeit.

This disclosure provides a security device including an array of lenses.The device can also include a plurality of first and second segmentsdisposed under the array of lenses. The first segments can correspond toportions of an icon and a background. At a first viewing angle, thearray of lenses presents the icon for viewing. At a second viewing angledifferent from the first viewing angle, the array of lenses does notpresent the icon for viewing. Individual ones of the first segments cancomprise specular reflecting features and diffusing features. Thespecular reflecting features can define one of the icon and thebackground. The diffusing features can define the background when thespecular reflecting features define the icon. The diffusing features candefine the icon when the specular reflecting features define thebackground. Individual ones of the second segments can comprisediffusing features when the diffusing features of the first segmentsdefine the background, and can comprise specular reflecting featureswhen the specular reflecting features of the first segments define thebackground.

Upon viewing at an angle in the specular direction, the icon can appeardark and the background can appear matte white or grey when the specularreflecting features define the icon and the diffusing features definethe background. Alternatively, upon viewing at an angle in the speculardirection, the icon can appear matte white or grey and the backgroundappears dark when the specular reflecting features define the backgroundand the diffusing features define the icon. The specular reflectingfeatures can define the icon and the diffusing features define thebackground.

At the first viewing angle, the array of lenses can present for viewingthe icon and the background. The background can comprise a shapedbackground. At the second viewing angle, the array of lenses can presentfor viewing the shaped background without the icon.

This disclosure provides a security device comprising an array oflenses. The device can include a plurality of first and second segmentsdisposed under the array of lenses. The first segments can correspond toportions of a first image, and the second segments can correspond toportions of a second image. The first and second images can comprise anicon and a background. At a first viewing angle, the array of lenses canpresent the first image for viewing without presenting the second imagefor viewing. At a second viewing angle different from the first viewingangle, the array of lenses can present for viewing the second imagewithout presenting the first image for viewing. Individual ones of thefirst and second segments can comprise specular reflecting features anddiffusing features. For the first and second segments, the specularreflecting features can define one of the icon and the background. Thediffusing features can define the background when the specularreflecting features define the icon. The diffusing features can definethe icon when the specular reflecting features define the background.

Upon viewing at an angle in the specular direction, the icon can appeardark and the background can appear matte white or grey when the specularreflecting features define the icon and the diffusing features definethe background. Alternatively, upon viewing at an angle in the speculardirection, the icon can appear matte white or grey and the backgroundcan appear dark when the specular reflecting features define thebackground and the diffusing features define the icon. For the first andsecond segments, the specular reflecting features can define the iconand the diffusing features can define the background. The icon of thefirst image can have a different overall shape than the icon of thesecond image.

This disclosure provides a security device comprising an array oflenses. The device can include a plurality of first and second segmentsdisposed under the array of lenses. The first segments can correspond toportions of a first icon and a first background. The second segments cancorrespond to portions of a second icon and a second background. At afirst viewing angle, the array of lenses can present for viewing thefirst icon and the first background without presenting the second iconfor viewing. At a second viewing angle different from the first viewingangle, the array of lenses can present for viewing the second icon andthe second background without presenting the first icon for viewing. Thesecond background at the second viewing angle can appear the same inouter shape, size, and brightness as the first background at the firstviewing angle. Individual ones of the first and second segments cancomprise specular reflecting features and diffusing features. For thefirst and second segments, the specular reflecting features can definethe first and second icons, and the diffusing features can define thefirst and second backgrounds. Alternatively, for the first and secondsegments, the diffusing features can define the first and second icons,and the specular reflecting features can define the first and secondbackgrounds.

Upon viewing at an angle in the specular direction, the first and secondicons can appear dark and the first and second backgrounds can appearmatte white or grey when the specular reflecting features define thefirst and second icons and the diffusing features define the first andsecond backgrounds. Alternatively, upon viewing at an angle in thespecular direction, the first and second icons can appear matte white orgrey and the first and second backgrounds can appear dark when thespecular reflecting features define the first and second backgrounds andthe diffusing features define the first and second icons.

For the first and second segments, the specular reflecting features candefine the first and second icons and the diffusing features can definethe first and second backgrounds. The first and second backgrounds canbe in the form of at least one alphanumeric character, a symbol, an artimage, graphic, or an object. The first and second backgrounds canfurther comprise a covert feature. For example, the covert feature cancomprise a fluorescent material or an up-converting pigment. The firstand second backgrounds can further comprise a tint, a dye, ink, or apigment.

This disclosure provides a security device comprising a plurality oflenses forming an array of lenses along a longitudinal axis. A pluralityof first and second segments can be disposed under the array of lenses.The first segments can correspond to portions of a first set of at leasttwo icons, and the second segments can correspond to portions of asecond set of at least two icons. At a first viewing angle, the array oflenses can present for viewing the first set of the at least two icons.At a second viewing angle different from the first viewing angle, thearray of lenses can present for viewing the second set of the at leasttwo icons.

The icons in the first and second sets can be separated by background.Also, one or more of the at least two icons of the first set can bedifferent from a corresponding one of the at least two icons of thesecond set. The first set and the second set can be presented forviewing in a row along the axis perpendicular to the longitudinal axisof the array of lenses.

This disclosure provides a security device comprising a plurality oflenses forming an array of lenses along a longitudinal axis. A pluralityof first and second segments can be disposed under the array of lenses.The first segments can correspond to portions of a first set of at leastfour icons, and the second segments can correspond to portions of asecond set of at least four icons. At a first viewing angle, the arrayof lenses can present for viewing the first set of the at least fouricons in a row along an axis perpendicular to the longitudinal axis ofthe array of lenses. At a second viewing angle different from the firstviewing angle, the array of lenses can present for viewing the secondset of the at least four icons in a row along the axis perpendicular tothe longitudinal axis of the array of lenses.

The icons in the first and second sets can be separated by background.One or more of the at least four icons of the first set can be differentfrom a corresponding one of the at least four icons of the second set.

This disclosure provides a security device comprising an array oflenses. A plurality of first and second segments can be disposed underthe array of lenses. The first segments can correspond to portions of afirst icon and a first background, and the second segments cancorrespond to portions of a second icon and a second background. At afirst viewing angle, the array of lenses can present for viewing thefirst icon and the first background without presenting the second iconfor viewing. At a second viewing angle different from the first viewingangle, the array of lenses can present for viewing the second icon andthe second background without presenting the first icon for viewing.Individual ones of the first segments can comprise a first surfacetexture defining the first icon. Individual ones of the second segmentscan comprise a second surface texture defining the second icon. Thesecond surface texture can be different from the first surface texture.Individual ones of the first and second segments can further comprise athird surface texture defining the first and second backgroundsrespectively. The third surface texture can be different from the firstand second surface textures.

The first surface texture can comprise a moth eye texture. The secondsurface texture can comprise an interference grating. The third surfacetexture can comprise a diffusing texture.

The first surface texture can comprise a moth eye texture. The secondsurface texture can comprise specular reflecting features. The thirdsurface texture comprises a diffusing texture.

The first surface texture can comprise specular reflecting features. Thesecond surface texture can comprise an interference grating. The thirdsurface texture can comprise a diffusing texture.

This disclosure provides a security device comprising a plurality oflenses forming an array of lenses. The lenses can have a longitudinalaxis disposed in a vertical direction. A plurality of first and secondsegments can be disposed under the array of lenses. The first segmentscan correspond to portions of a right side view of an image, and thesecond segments can correspond to portions of a left side view of theimage. The image can comprise an icon and a background. When tilting thefirst and second segments about the longitudinal axis of the lenses, thearray of lenses can present the right and left side views of the imagefor a stereoscopic view of the image. Individual ones of the first andsecond segments can comprise specular reflecting features and diffusingfeatures. For the first and second segments, the specular reflectingfeatures can define one of the icon and the background. The diffusingfeatures can define the background when the specular reflecting featuresdefine the icon. The diffusing features can define the icon when thespecular reflecting features define the background.

The specular reflecting features can define the icon and the diffusingfeatures can define the background. The first and second segments cancorrespond to portions of at least three images.

This disclosure provides the following features in a security device.

The array of lenses can comprise a 1D lenticular lens array. The arrayof lenses can comprise a 2D array of lenses. For example, the array oflenses can comprise a first lenticular lens array having a firstlongitudinal axis and a second lenticular lens array having a secondlongitudinal axis. The first and second arrays can be arranged such thatthe first longitudinal axis of the first array is angled from 5 to 90degrees with respect to the second longitudinal axis of the secondarray. A difference in the first and second viewing angles can be lessthan or equal to 15 degrees under a point light source. A difference inthe first and second viewing angles can be less than or equal to 20degrees under an extended light source.

A first image or icon or set of icons can flip to the second image oricon or set of icons with no observable transition upon a change fromthe first viewing angle to the second viewing angle.

The first and second segments can each comprise a length, a width, and athickness. The width of each of the first and second segments can beless than or equal to 80 microns.

The first image or second image, the icon, first or second icon, or thefirst or second set can comprise a half tone image.

The contrast percentage between the icon and the background, between thefirst icon and the first background, or between the second icon and thesecond background can be from 25% to 90% when viewing at an angle in thespecular direction, or from 25% to 90% when viewing at an angle not inthe specular direction.

For the first or second segments, the diffusing features can provideLambertian reflectance.

For the first or second segments, the diffusing features can have anelliptical output.

The device can comprise a kinoform diffuser providing the diffusingfeatures.

For the first or second segments, the diffusing features can comprise abrightness greater than 85 and a whiteness index greater than 85.

For the first or second segments, the diffusing features can compriseTiO₂ particles.

For the first or second segments, the specular reflecting features andthe diffusing features can provide no diffractive or interference color.

For the first or second segments, the diffusing features can comprise atint, an ink, a fluorescent chemical, a transparent dye, an opaque dye,or an opaque pigment.

The icon, first or second image, first or second icon, or first orsecond set can comprise at least one alphanumeric character, a symbol,an art image, graphic, or an object. The background of the icon, thebackground of the first or second image, or the background of the firstor second icon can comprise a circle, a square, a rectangle, a hexagon,an oval, a star, or a knurled edge. The background of the icon, thebackground of the first or second image, or the background of the firstor second icon can comprise a pattern of alphanumeric characters,symbols, images, graphics, or objects.

The security device can further comprise a substrate having a first sideand a second side opposite the first side. The array of lenses can bedisposed on the first side of the substrate. The specular reflectingfeatures and diffusing features can be disposed on the second side ofthe substrate. The substrate can have a thickness in a range from 10microns to 300 microns. The thickness can be in the range from 10microns to 90 microns, from 10 microns to 85 microns, from 10 microns to70 microns, from 10 microns to 60 microns, from 10 microns to 50microns, from 10 microns to 45 microns, from 10 microns to 40 microns,in any ranges within these ranges, any values within these ranges, or inany ranges formed by such values.

The security device can be configured to provide authenticityverification on an item for security. The item can be a credit card, adebit card, currency, a passport, a driver's license, an identificationcard, a document, a temper evident container or packaging, or a bottleof pharmaceuticals. The security device can be a security thread, a hotstamp feature, an embedded feature, a windowed feature, or a laminatedfeature.

The security device can further comprise another optical element outsideof the first and second segments. The security device can furthercomprise another optical element within of the first segment or thesecond segment. The another optical element can comprise a holographicelement, a diffractive element, or a non-holographic non-diffractiveelement.

The security device can further comprise one or more micro-structurallenses. The one or more micro-structural lenses can comprise a Fresnellens or a diamond turned element. The one or more micro-structurallenses can be overprinted.

The security device can further comprise a metallized coating. Thesecurity device can further comprise a metallized coating with portionswithout metallization to form at least one alphanumeric character, asymbol, an image, or an object. The metallized coating can comprisealuminum, silver, gold, copper, titanium, zinc, tin, or any alloythereof.

The background for the first or second image, the background for theicon, or the first or second background can be transparent.

For the first or second segments, the diffusing features can be coatedwith a transparent high index material. For the first or secondsegments, the diffusing features can be coated with ZnS.

The first segment can comprise half tone. The second segment cancomprise half tone. The specular reflecting features and the diffusingfeatures can each have sizes and be distributed within the first orsecond segment to provide half tone imagery for producing the icon, thefirst or second image, the first or second icon, or the first or secondset.

The specular reflecting features and the diffusing features can beincluded in the first or second segment in an amount and distribution toprovide half tone imagery for producing the icon, the first or secondimage, the first or second icon, or the first or second set.

The first or second segment can include specular reflecting featuresthat provide half tone, where individual specular reflecting featurescannot be resolved in images of the specular reflecting featuresproduced by a corresponding lens in the array of lenses by the unaidedeye.

The shape of the icon, the shape of the first or second image, the shapeof the first or second icon, or the shape of the first or second set canbe invariant as the light source changes position.

The first or second segment can comprise a micro-image having a heightsmaller than a width of the first or second segment. The micro-image canbe at least one alphanumeric character, symbol, an art image, graphic,or an object.

This disclosure provides a method of fabricating a security device. Themethod can comprise preparing a master using an electron beam,lithographic techniques, or etching. The method can further compriseusing the master to form the specular reflecting features or thediffusing features.

Various embodiments disclosed herein can be used for security documents,in particular, as security threads in bank notes or as a laminatedstrip, or as a patch or as a window. Other security items such aspassports, ID cards, chip cards, credit cards, stock certificates andother investment securities, vouchers, admission tickets and commercialpackages that protect items of value such as CD's, medicinal drugs, carand aircraft parts, etc. may also be protected against counterfeitingusing the concepts and embodiments described herein. Furthermore,various embodiments disclosed herein can also be used for non-securityapplications.

Additional examples are provided below.

1. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        an icon and a background,    -   wherein at a first viewing angle, the array of lenses presents        the icon for viewing, and at a second viewing angle different        from the first viewing angle, the array of lenses does not        present the icon for viewing,    -   wherein individual ones of the first segments comprise specular        reflecting features and diffusing features, the specular        reflecting features defining one of the icon and the background,        the diffusing features defining the background when the specular        reflecting features define the icon, and the diffusing features        defining the icon when the specular reflecting features define        the background, and    -   wherein individual ones of the second segments comprise        diffusing features when the diffusing features of the first        segments define the background, and comprise specular reflecting        features when the specular reflecting features of the first        segments define the background.

2. The security device of Example 1, wherein upon viewing at an angle inthe specular direction,

-   -   the icon appears dark and the background appears matte white or        grey when the specular reflecting features define the icon and        the diffusing features define the background, or    -   the icon appears matte white or grey and the background appears        dark when the specular reflecting features define the background        and the diffusing features define the icon.

3. The security device of Example 1 or 2, wherein for the firstsegments, the specular reflecting features define the icon and thediffusing features define the background.

4. The security device of any of Examples 1-3, wherein at the firstviewing angle, the array of lenses presents for viewing the icon and thebackground, the background comprising a shaped background, and whereinat the second viewing angle, the array of lenses presents for viewingthe shaped background without the icon.

5. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first image, and the second segments corresponding to portions        of a second image, the first and second images comprising an        icon and a background,    -   wherein at a first viewing angle, the array of lenses presents        the first image for viewing without presenting the second image        for viewing, and at a second viewing angle different from the        first viewing angle, the array of lenses presents for viewing        the second image without presenting the first image for viewing,    -   wherein individual ones of the first and second segments        comprise specular reflecting features and diffusing features,        and    -   wherein for the first and second segments, the specular        reflecting features define one of the icon and the background,        the diffusing features define the background when the specular        reflecting features define the icon, and the diffusing features        define the icon when the specular reflecting features define the        background.

6. The security device of Example 5, wherein upon viewing at an angle inthe specular direction,

-   -   the icon appears dark and the background appears matte white or        grey when the specular reflecting features define the icon and        the diffusing features define the background, or    -   the icon appears matte white or grey and the background appears        dark when the specular reflecting features define the background        and the diffusing features define the icon.

7. The security device of Example 5 or 6, wherein for the first andsecond segments, the specular reflecting features define the icon andthe diffusing features define the background.

8. The security device of any of Examples 5-8, wherein the icon of thefirst image has a different overall shape than the icon of the secondimage.

9. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first icon and a first background, and the second segments        corresponding to portions of a second icon and a second        background,    -   wherein at a first viewing angle, the array of lenses presents        for viewing the first icon and the first background without        presenting the second icon for viewing, and at a second viewing        angle different from the first viewing angle, the array of        lenses presents for viewing the second icon and the second        background without presenting the first icon for viewing,    -   wherein the second background at the second viewing angle        appears the same in outer shape, size, and brightness as the        first background at the first viewing angle,    -   wherein individual ones of the first and second segments        comprise specular reflecting features and diffusing features,    -   wherein for the first and second segments,        -   the specular reflecting features define the first and second            icons, and the diffusing features define the first and            second backgrounds, or        -   the diffusing features define the first and second icons,            and the specular reflecting features define the first and            second backgrounds.

10. The security device of Example 9, wherein upon viewing at an anglein the specular direction,

-   -   the first and second icons appear dark and the first and second        backgrounds appear matte white or grey when the specular        reflecting features define the first and second icons and the        diffusing features define the first and second backgrounds, or    -   the first and second icons appear matte white or grey and the        first and second backgrounds appear dark when the specular        reflecting features define the first and second backgrounds and        the diffusing features define the first and second icons.

11. The security device of Example 9 or 10, wherein for the first andsecond segments, the specular reflecting features define the first andsecond icons and the diffusing features define the first and secondbackgrounds.

12. The security device of any of Examples 9-11, wherein the first andsecond backgrounds are in the form of at least one alphanumericcharacter, a symbol, an art image, graphic, or an object.

13. The security device of any of Examples 9-12, wherein the first andsecond backgrounds further comprise a covert feature.

14. The security device of Example 13, wherein the covert featurecomprises a fluorescent material or an up-converting pigment.

15. The security device of any of Examples 9-14, wherein the first andsecond backgrounds further comprise a tint, a dye, ink, or a pigment.

16. A security device comprising:

-   -   a plurality of lenses forming an array of lenses along a        longitudinal axis; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first set of at least two icons, and the second segments        corresponding to portions of a second set of at least two icons,    -   wherein at a first viewing angle, the array of lenses presents        for viewing the first set of the at least two icons, and at a        second viewing angle different from the first viewing angle, the        array of lenses presents for viewing the second set of the at        least two icons,    -   wherein one or more of the at least two icons of the first set        are different from a corresponding one of the at least two icons        of the second set.

17. The security device of Example 16, the first set and the second setare presented for viewing in a row along the axis perpendicular to thelongitudinal axis of the array of lenses.

18. A security device comprising:

-   -   a plurality of lenses forming an array of lenses along a        longitudinal axis; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first set of at least four icons, and the second segments        corresponding to portions of a second set of at least four        icons,    -   wherein at a first viewing angle, the array of lenses presents        for viewing the first set of the at least four icons in a row        along an axis perpendicular to the longitudinal axis of the        array of lenses, and at a second viewing angle different from        the first viewing angle, the array of lenses presents for        viewing the second set of the at least four icons in a row along        the axis perpendicular to the longitudinal axis of the array of        lenses,

19. The security device of Example 18, wherein one or more of the atleast four icons of the first set are different from a corresponding oneof the at least four icons of the second set.

20. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first icon and a first background, and the second segments        corresponding to portions of a second icon and a second        background,    -   wherein at a first viewing angle, the array of lenses presents        for viewing the first icon and the first background without        presenting the second icon for viewing, and at a second viewing        angle different from the first viewing angle, the array of        lenses presents for viewing the second icon and the second        background without presenting the first icon for viewing,    -   wherein individual ones of the first segments comprise a first        surface texture defining the first icon,    -   wherein individual ones of the second segments comprise a second        surface texture defining the second icon, the second surface        texture different from the first surface texture,    -   wherein individual ones of the first and second segments further        comprise a third surface texture defining the first and second        backgrounds respectively, the third surface texture different        from the first and second surface textures.

21. The security device of Example 20, wherein the first surface texturecomprises a moth eye texture, the second surface texture comprises aninterference grating, and the third surface texture comprises adiffusing texture.

22. The security device of Example 20, wherein the first surface texturecomprises a moth eye texture, the second surface texture comprisesspecular reflecting features, and the third surface texture comprises adiffusing texture.

23. The security device of Example 20, wherein the first surface texturecomprises specular reflecting features, the second surface texturecomprises an interference grating, and the third surface texturecomprises a diffusing texture.

24. A security device comprising:

-   -   a plurality of lenses forming an array of lenses, the lenses        having a longitudinal axis disposed in a vertical direction; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a right side view of an image, and the second segments        corresponding to portions of a left side view of the image, the        image comprising an icon and a background,    -   wherein when tilting the first and second segments about the        longitudinal axis of the lenses, the array of lenses presents        the right and left side views of the image for a stereoscopic        view of the image,    -   wherein individual ones of the first and second segments        comprise specular reflecting features and diffusing features,        and    -   wherein for the first and second segments, the specular        reflecting features define one of the icon and the background,        the diffusing features define the background when the specular        reflecting features define the icon, and the diffusing features        define the icon when the specular reflecting features define the        background.

25. The security device of Example 24, wherein the specular reflectingfeatures define the icon and the diffusing features define thebackground.

26. The security device of Example 24 or 25, wherein the first andsecond segments correspond to portions of at least three images.

27. The security device of any of the preceding examples, wherein thearray of lenses comprises a 1D lenticular lens array.

28. The security device of any of the preceding examples, wherein thearray of lenses comprises a 2D array of lenses.

29. The security device of Example 28, wherein the array of lensescomprises a first lenticular lens array having a first longitudinal axisand a second lenticular lens array having a second longitudinal axis,wherein the first and second arrays are arranged such that the firstlongitudinal axis of the first array is angled from 5 to 90 degrees withrespect to the second longitudinal axis of the second array.

30. The security device of any of the preceding examples, wherein adifference in the first and second viewing angles is less than or equalto 15 degrees under a point light source.

31. The security device of any of the preceding examples, wherein adifference in the first and second viewing angles is less than or equalto 20 degrees under an extended light source.

32. The security device of any of Examples 5-8, wherein the first imageflips to the second image with no observable transition upon a changefrom the first viewing angle to the second viewing angle.

33. The security device of any of Examples 9-15 or any of Examples20-23, wherein the first icon flips to the second icon with noobservable transition upon a change from the first viewing angle to thesecond viewing angle.

34. The security device of any of Examples 16-19, wherein the first setflips to the second set with no observable transition upon a change fromthe first viewing angle to the second viewing angle.

35. The security device of any of the preceding examples, wherein thefirst and second segments each comprises a length, a width, and athickness, and wherein the width of each of the first and secondsegments is less than or equal to 80 microns.

36. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the icon comprises a half tone image.

37. The security device of any of Examples 5-8, wherein the first orsecond image comprises a half tone image.

38. The security device of any of Examples 9-15 or any of Examples20-23, wherein the first or second icon comprises a half tone image.

39. The security device of any of Examples 16-19, wherein the first orsecond set comprises a half tone image.

40. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the contrast percentage between the icon and the background isfrom 25% to 90% when viewing at an angle in the specular direction, orfrom 25% to 90% when viewing at an angle not in the specular direction.

41. The security device of any of Examples 5-8, wherein for the firstimage or the second image, the contrast percentage between the icon andthe background is from 25% to 90% when viewing at an angle in thespecular direction, or from 25% to 90% when viewing at an angle not inthe specular direction.

42. The security device of any of Examples 9-15 or any of Examples20-23, wherein the contrast percentage between the first icon and thefirst background or between the second icon and the second background isfrom 25% to 90% when viewing at an angle in the specular direction, orfrom 25% to 90% when viewing at an angle not in the specular direction.

43. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featuresprovide Lambertian reflectance.

44. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featureshave an elliptical output.

45. The security device of any of Examples 1-15 or any of Examples24-26, wherein the device comprises a kinoform diffuser providing thediffusing features.

46. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featurescomprise a brightness greater than 85 and a whiteness index greater than85.

47. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featurescomprise TiO₂ particles.

48. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the specular reflectingfeatures and the diffusing features provide no diffractive orinterference color.

49. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featurescomprise a tint, an ink, a fluorescent chemical, a transparent dye, anopaque dye, or an opaque pigment.

50. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the icon comprises at least one alphanumeric character, asymbol, an art image, graphic, or an object.

51. The security device of any of Examples 5-8, wherein the first orsecond image comprises at least one alphanumeric character, a symbol, anart image, graphic, or an object.

52. The security device of any of Examples 9-15 or any of Examples20-23, wherein the first or second icon comprises at least onealphanumeric character, a symbol, an art image, graphic, or an object.

53. The security device of any of Examples 16-19, wherein the first orsecond set comprises at least one alphanumeric character, a symbol, anart image, graphic, or an object.

54. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the background of the icon comprises a circle, a square, arectangle, a hexagon, an oval, a star, or a knurled edge.

55. The security device of any of Examples 5-8, wherein the backgroundof the first or second image comprises a circle, a square, a rectangle,a hexagon, an oval, a star, or a knurled edge.

56. The security device of any of Examples 9-15 or any of Examples20-23, wherein the background of the first or second icon comprises acircle, a square, a rectangle, a hexagon, an oval, a star, or a knurlededge.

57. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the background of the icon comprises a pattern of alphanumericcharacters, symbols, images, graphics, or objects.

58. The security device of any of Examples 5-8, wherein the backgroundof the first or second image comprises a pattern of alphanumericcharacters, symbols, images, graphics, or objects.

59. The security device of any of Examples 9-15 or any of Examples20-23, wherein the background of the first or second icon comprises apattern of alphanumeric characters, symbols, images, graphics, orobjects.

60. The security device of any of Examples 1-15 or any of Examples24-26, further comprising a substrate having a first side and a secondside opposite the first side,

-   -   wherein the array of lenses is disposed on the first side of the        substrate, and    -   wherein the specular reflecting features and diffusing features        are disposed on the second side of the substrate.

61. The security device of Example 60, wherein the substrate has athickness in a range from 10 microns to 300 microns.

62. The security device of Example 61, wherein the thickness is in therange from 10 microns to 40 microns.

63. The security device of any of the preceding examples, wherein thesecurity device is configured to provide authenticity verification on anitem for security.

64. The security device of Example 63, wherein the item is a creditcard, a debit card, currency, a passport, a driver's license, anidentification card, a document, a temper evident container orpackaging, or a bottle of pharmaceuticals.

65. The security device of any of the preceding examples, wherein thesecurity device is a security thread, a hot stamp feature, an embeddedfeature, a windowed feature, or a laminated feature.

66. The security device of any of the preceding examples, furthercomprising another optical element outside of the first and secondsegments.

67. The security device of any of the preceding examples, furthercomprising another optical element within of the first segment or thesecond segment.

68. The security device of Example 67, wherein the another opticalelement comprises a holographic element, a diffractive element, or anon-holographic non-diffractive element.

69. The security device of any of the preceding examples, furthercomprising one or more micro-structural lenses.

70. The security device of Example 69, wherein the one or moremicro-structural lenses comprise a Fresnel lens or a diamond turnedelement.

71. The security device of Example 69 or 70, wherein the one or moremicro-structural lenses are overprinted.

72. The security device of any of the preceding examples, furthercomprising a metallized coating.

73. The security device of any of the preceding examples, furthercomprising a metallized coating with portions without metallization toform at least one alphanumeric character, a symbol, an image, or anobject.

74. The security device of Example 72 or 73, wherein the metallizedcoating comprises aluminum, silver, gold, copper, titanium, zinc, tin,or any alloy thereof.

75. The security device of any of Examples 5-8, wherein for the first orsecond image, the background is transparent.

76. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the background is transparent.

77. The security device of any of Examples 9-15 or any of Examples20-23, wherein the first or second background is transparent.

78. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featuresare coated with a transparent high index material.

79. The security device of any of Examples 1-15 or any of Examples24-26, wherein for the first or second segments, the diffusing featuresare coated with ZnS.

80. The security device of any of the preceding examples, wherein thefirst segment comprises half tone.

81. The security device of any of the preceding examples, wherein thesecond segment comprises half tone.

82. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the specular reflecting features and the diffusing features eachhave sizes and are distributed within said first or second segment toprovide half tone imagery for producing said icon.

83. The security device of any of Examples 5-8, wherein the specularreflecting features and the diffusing features each have sizes and aredistributed within said first or second segment to provide half toneimagery for producing said first or second image.

84. The security device of any of Examples 9-15 or any of Examples20-23, wherein the specular reflecting features and the diffusingfeatures each have sizes and are distributed within said first or secondsegment to provide half tone imagery for producing said first or secondicon.

85. The security device of any of Examples 16-19, wherein the specularreflecting features and the diffusing features each have sizes and aredistributed within said first or second segment to provide half toneimagery for producing said first or second set.

86. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the specular reflecting features and the diffusing features areincluded in said first or second segment in an amount and distributionto provide half tone imagery for producing said icon.

87. The security device of any of Examples 5-8, wherein the specularreflecting features and the diffusing features are included in saidfirst or second segment in an amount and distribution to provide halftone imagery for producing said first or second image.

88. The security device of any of Examples 9-15 or any of Examples20-23, wherein the specular reflecting features and the diffusingfeatures are included in said first or second segment in an amount anddistribution to provide half tone imagery for producing said first orsecond icon.

89. The security device of any of Examples 16-19, wherein the specularreflecting features and the diffusing features are included in saidfirst or second segment in an amount and distribution to provide halftone imagery for producing said first or second set.

90. The security device of any of the preceding examples, wherein thefirst or second segment includes specular reflecting features thatprovide half tone, wherein individual specular reflecting featurescannot be resolved in images of the specular reflecting featuresproduced by a corresponding lens in the array of lenses by the unaidedeye.

91. The security device of any of Examples 1-4 or any of Examples 24-26,wherein the shape of the icon is invariant as the light source changesposition.

92. The security device of any of Examples 5-8, wherein the shape of thefirst or second image is invariant as the light source changes position.

93. The security device of any of Examples 9-15 or any of Examples20-23, wherein the shape of the first or second icon is invariant as thelight source changes position.

94. The security device of any of Examples 16-19, wherein the shape ofthe first or second set is invariant as the light source changesposition.

95. The security device of any of the preceding examples, wherein thefirst or second segment comprises a micro-image having a height smallerthan a width of the first or second segment.

96. The security device of Example 95, wherein the micro-image is atleast one alphanumeric character, symbol, an art image, graphic, or anobject.

97. The security device of any of Examples 16-19, wherein the icons inthe first and second sets are separated by background.

98. A method of fabricating a security device of any of the precedingexamples, the method comprising:

-   -   preparing a master using an electron beam, lithographic        techniques, or etching; and    -   using the master to form the specular reflecting features or the        diffusing features.

99. The security device of any of Examples 1-97, wherein at least onefirst segment or at least one second segment comprises one or moremicrostructures or one or more nanostructures configured to provide oneor more colors.

100. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        an icon and a background,    -   wherein at a first viewing angle, the array of lenses presents a        view of the icon, and at a second viewing angle different from        the first viewing angle, the array of lenses presents a view        without the icon, and    -   wherein at least one first segment or at least one second        segment comprises one or more microstructures or one or more        nanostructures configured to provide one or more colors for the        view of the icon or the view without the icon.

101. The security device of Example 100, wherein the at least one firstsegment comprises the one or more microstructures or the one or morenanostructures configured to provide one or more colors for the icon orfor the background.

102. The security device of Example 100 or 101, wherein the at least onesecond segment comprises the one or more microstructures or the one ormore nanostructures configured to provide one or more colors for theview without the icon.

103. A security device comprising:

-   -   an array of lenses; and    -   a plurality of first and second segments disposed under the        array of lenses, the first segments corresponding to portions of        a first image, and the second segments corresponding to portions        of a second image,    -   wherein at a first viewing angle, the array of lenses presents        the first image for viewing without presenting the second image        for viewing, and at a second viewing angle different from the        first viewing angle, the array of lenses presents for viewing        the second image without presenting the first image for viewing,        and    -   wherein at least one first segment or at least one second        segment of the plurality of first and second segments comprises        one or more microstructures or one or more nanostructures        configured to provide one or more colors for the first or second        image.

104. The security device of Example 103, wherein the first and secondimages comprise an icon and a background.

105. The security device of Example 104, wherein the icon of the firstimage has a different overall shape than the icon of the second image.

106. The security device of any of Example 103-105, wherein the at leastone first segment and the at least one second segment comprise the oneor more microstructures or the one or more nanostructures.

107. The security device of Example 106, wherein the one or moremicrostructures or the one or more nanostructures are configured toprovide a first color for the first image and a second color for thesecond image.

108. The security device of Example 107, wherein the first and secondcolors are different.

109. The security device of any of Examples 99-108, wherein the one ormore microstructures or the one or more nanostructures comprise at leastone opal structure.

110. The security device of Example 109, wherein the at least one opalstructure comprises a plurality of microsurface or nanosurface reliefportions.

111. The security device of Example 110, wherein the microsurface ornanosurface relief portions comprise a reflective metal coating.

112. The security device of Example 110, wherein the microsurface ornanosurface relief portions comprise a transparent coating having anindex of refraction between 1.8 and 3.

113. The security device of Example 112, wherein the transparent coatingcomprises zinc sulfide, titanium oxide, or indium tin oxide.

114. The security device of any of Examples 99-113, wherein the one ormore microstructures or the one or more nanostructures comprise at leastone plasmonic structure.

115. The security device of Example 114, wherein the at least oneplasmonic structure comprises:

-   -   a first metal microfeature or nanofeature;    -   a second metal microfeature or nanofeature; and    -   a dielectric microfeature or nanofeature.

116. The security device of Example 115, wherein the first or secondmetal microfeature or nanofeature comprises silver, aluminum, gold,copper, tin, or combinations thereof.

117. The security device of Example 115 or Example 116, wherein thedielectric microfeature or nanofeature comprises a dielectric materialbetween the first and second metal microfeature or nanofeature.

118. The security device of Example 117, wherein the dielectric materialcomprises a UV curable resin.

119. The security device any of Examples 115-118, wherein the dielectricmicrofeature or nanofeature comprises a reflective microfeature ornanofeature disposed over the dielectric microfeature or nanofeature.

120. The security device of Example 119, wherein the reflectivemicrofeature or nanofeature comprises aluminum.

121. The security device of Example 119 or Example 120, furthercomprising a protective coating over the reflective microfeature ornanofeature.

122. The security device of any of Examples 115-121, wherein the atleast one plasmonic structure does not comprise a reflectivemicrofeature or nanofeature disposed on the dielectric microfeature ornanofeature.

123. The security device of any of Examples 99-122, wherein the one ormore colors produced by a corresponding lens in the array of lenses canbe resolved by an unaided eye.

124. The security device of any of Examples 99-123, wherein at least oneof the one or more colors produced by a corresponding lens in the arrayof lens cannot be resolved by an unaided eye.

125. The security device of any of Examples 99-124, wherein the one ormore microstructures or the one or more nanostructures comprise aplurality of microstructures, nanostructures, or combinations thereof.

126. The security device of any of Examples 99-125, wherein the one ormore microstructures or the one or more nanostructures are configured toprovide a same color.

127. The security device of any of Examples 99-125, wherein the one ormore microstructures or the one or more nanostructures are configured toprovide different colors.

128. The security device of Example 127, wherein the one or moremicrostructures or the one or more nanostructures are configured toprovide different colors that combine to produce a single color asperceived by the naked eye.

129. The security device of Example 127, wherein the one or moremicrostructures or the one or more nanostructures are configured toprovide different colors that combine to produce an achromatic whiteappearance.

130. The security device of any of Examples 100-129, wherein the arrayof lenses comprises a 1D lenticular lens array.

131. The security device of any of Examples 100-129, wherein the arrayof lenses comprises a 2D array of lenses.

132. The security device of any of Examples 100-131, wherein one of thefirst segments of the plurality of first segments comprises diffusingfeatures.

133. The security device of any of Examples 100-132, wherein one of thesecond segments of the plurality of second segments comprises diffusingfeatures.

134. The security device of Example 132 or 133, wherein the diffusingfeatures provide Lambertian reflectance.

135. The security device of any of Examples 132-134, wherein thediffusing features have an elliptical output.

136. The security device of any of Examples 132-135, wherein the devicecomprises a kinoform diffuser providing the diffusing features.

137. The security device of any of Examples 132-136, wherein thediffusing features comprise a brightness greater than 85 and a whitenessindex greater than 85.

138. The security device of any of Examples 100-137, wherein one of thefirst segments of the plurality of first segments comprises specularreflecting features.

139. The security device of any of Examples 100-138, wherein one of thesecond segments of the plurality of second segments comprises specularreflecting features.

140. The security device of any of Examples 100-102, wherein the iconcomprises a half tone image.

141. The security device of any of Examples 103-108, wherein the firstor second image comprises a half tone image.

142. The security device of any of Examples 100-102 or Example 140,wherein the icon comprises at least one alphanumeric character, asymbol, an art image, graphic, or an object.

143. The security device of any of Examples 103-108 or Example 141,wherein the first or second image comprises at least one alphanumericcharacter, a symbol, an art image, graphic, or an object.

144. The security device of any of Examples 100-102 or Example 140 orExample 142, wherein the background of the icon comprises a circle, asquare, a rectangle, a hexagon, an oval, a star, or a knurled edge.

145. The security device of any of Examples 103-108 or Example 141 orExample 143, wherein the background of the first or second imagecomprises a circle, a square, a rectangle, a hexagon, an oval, a star,or a knurled edge.

146. The security device of any of Examples 100-102 or Example 140 orExample 142, wherein the background of the icon comprises a pattern ofalphanumeric characters, symbols, images, graphics, or objects.

147. The security device of any of Examples 103-108 or Example 141 orExample 143, wherein the background of the first or second imagecomprises a pattern of alphanumeric characters, symbols, images,graphics, or objects.

148. The security device of any of Examples 130-147, further comprisinga substrate having a first side and a second side opposite the firstside,

-   -   wherein the array of lenses is disposed on the first side of the        substrate, and    -   wherein the one or more microstructures or the one or more        nanostructures are disposed on the second side of the substrate.

149. The security device of any of Examples 100-148, wherein thesecurity device is configured to provide authenticity verification on anitem for security.

150. The security device of Example 149, wherein the item is a creditcard, a debit card, currency, a passport, a driver's license, anidentification card, a document, a temper evident container orpackaging, or a bottle of pharmaceuticals.

151. The security device of any of Examples 100-150, wherein thesecurity device is a security thread, a hot stamp feature, an embeddedfeature, a windowed feature, or a laminated feature.

152. The security device of any of Examples 100-151, further comprisinganother optical element outside of the first and second segments.

153. The security device of any of Examples 100-152, further comprisinganother optical element within of the first segment or the secondsegment.

154. The security device of Example 152 or Example 153, wherein theanother optical element comprises a holographic element, a diffractiveelement, or a non-holographic non-diffractive element.

155. The security device of any of Examples 100-154, wherein a first orsecond segment comprises half tone.

156. The method of Example 98, further comprising using the master toform one or more microstructure or one or more nanostructures configuredto provide one or more colors.

157. A method of fabricating a security device of any of Examples99-155, the method comprising:

-   -   preparing a master using an electron beam, lithographic        techniques, or etching; and    -   using the master to form the one or more microstructures or the        one or more nanostructures.

158. The method of Example 157, further comprising using the master toform one or more specular reflecting features or diffusing features.

159. The security device of any of Examples 109-155, wherein the atleast one opal structure comprises at least one reverse opal structure.

160. The security device of any of Examples 109-155 or Example 159,wherein the at least one opal structure comprises at least one positiveopal structure.

161. The security device of any of Examples 109-155 or any of Examples159-160, wherein the at least one opal structure comprises at least onereflective opal structure.

162. The security device of any of Examples 109-155 or any of Examples159-161, wherein the at least one opal structure comprises at least onetransmissive opal structure.

163. The security device of any of Examples 114-155 or any of Examples159-162, wherein the at least one plasmonic structure comprises at leastone reflective plasmonic structure

164. The security device of any of Examples 114-155 or any of Examples159-163, wherein the at least one plasmonic structure comprises at leastone transmissive plasmonic structure.

165. The security device of any of Examples 99-155 or any of Examples159-164, wherein the device is configured to provide a rendition of anobject's natural color through an icon or image.

166. The security device of any of Examples 1-97 or any of Examples99-155 or any of Examples 159-165, further comprising one or moremicrostructures or one or more nanostructures configured to provide oneor more colors in a region other than said plurality of first and secondsegments disposed under the array of lenses.

167. The security device of Example 28, wherein the plurality of firstand second segments form a 2D image array, wherein each of the pluralityof first and second segments is disposed with respect to a correspondinglens of the 2D array of lenses.

168. The security device of Example 167, wherein the 2D array of lensesis registered with the 2D image array such that a distance betweenadjacent lenses of the 2D array of lenses is equal to a distance betweenthe corresponding segments that are disposed under the 2D array oflenses.

169. The security device of Example 167, wherein a distance betweenadjacent lenses of the 2D array of lenses is less than or greater than adistance between the corresponding segments that are disposed under the2D array of lenses such that pitch of the 2D array of lenses is notequal to pitch of the 2D image array.

170. The security device of Example 167, wherein the icon appear to movelaterally when the device is tilted such that the viewing angle changesfrom the first viewing angle to the second viewing angle.

171. The security device of Example 167, wherein the icon appear at thesurface of the device or appear to float above or below the surface ofthe device in the first or the second viewing angle.

172. A security device comprising:

-   -   a plurality of lenses forming an array of lenses along a        longitudinal axis; and    -   a plurality of portions disposed under the array of lenses, the        plurality of portions comprising two icons,    -   wherein at a first viewing angle, the array of lenses presents        for viewing the first icon at a first position and the second        icon at a second position and at a second viewing angle        different from the first viewing angle, the array of lenses        presents for viewing the second icon at a third position        different from the second position.

173. The security device of Example 172, wherein at the second viewingangle, the array of lenses presents for viewing the first icon at afourth position different from the first position.

174. The security device of Example 173, wherein at the second viewingangle, the first icon appears to move from the first position to thefourth position along a first direction and the second icon appears tomove from the second position to the third position along a seconddirection different from the first direction.

175. The security device of Example 173, wherein at the second viewingangle, the first icon appears to move from the first position to thefourth position along a first direction and the second icon appears tomove from the second position to the third position along the firstdirection.

176. The security device of Example 172, wherein at the second viewingangle, the second icon appears to move closer to the first icon.

177. The security device of Example 172, wherein at the second viewingangle, the second icon appears to move farther from the first icon.

178. The security device of any of Examples 172-177, wherein at leastone of the plurality of portions comprises one or more microstructuresor one or more nanostructures configured to provide one or more colors.

179. The security device of Example 178, wherein the one or moremicrostructures or the one or more nanostructures comprise at least oneopal structure.

180. The security device of Example 179, wherein the at least one opalstructure comprises at least one reverse opal structure.

181. The security device of Example 179 or Example 180, wherein the atleast one opal structure comprises at least one positive opal structure.

182. The security device of any of Examples 178-181, wherein the one ormore microstructures or the one or more nanostructures comprise at leastone plasmonic structure.

183. The security device of any of Examples 172-177, wherein theplurality of portions comprise a first set of specular reflectingfeatures or diffusing features defining the first icon and second set ofspecular reflecting features or diffusing features defining the secondicon.

184. The security device of any of Examples 172-177, wherein theplurality of lenses are arranged to form a two-dimensional lens grid andthe plurality of portions are arranged to form a two-dimensional imagegrid such that each lens of the lens grid is disposed over acorresponding portion of the image grid, and wherein distance betweenconsecutive portions of the image grid is not equal to distance betweenthe corresponding lenses of the lens grid disposed over the consecutiveportions.

185. The security device of any of Examples 172-177, wherein theplurality of lenses are arranged to form a two-dimensional lens grid andthe plurality of portions are arranged to form a two-dimensional imagegrid such that each lens of the lens grid is disposed over acorresponding portion of the image grid, and wherein the lens grid isrotated with respect to the image grid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A schematically illustrates an example security device inaccordance with certain embodiments described herein.

FIG. 1B schematically illustrates certain features of the examplesecurity device shown in FIG. 1A.

FIG. 1C-1 schematically illustrates a 1D lens array compatible withcertain embodiments described herein.

FIG. 1C-2 schematically illustrates a 2D lens array compatible withcertain embodiments described herein.

FIG. 2A schematically illustrates viewing at an angle in the speculardirection of specular reflecting features and at the same angle ofdiffusing features in accordance with certain embodiments describedherein.

FIG. 2B schematically illustrates viewing at angles not in the speculardirection of specular reflecting features and at the same angles ofdiffusing features in accordance with certain embodiments describedherein.

FIG. 2C schematically illustrates certain images and effects that can bepresented during viewing at an angle in the specular direction by asecurity device in accordance with certain embodiments described herein.

FIG. 2D schematically illustrates certain images and effects that can bepresented during viewing at an angle not in the specular direction by asecurity device in accordance with certain embodiments described herein.

FIG. 3A schematically illustrates another example security device inaccordance with certain embodiments described herein.

FIG. 3B schematically illustrates certain features of the examplesecurity device shown in FIG. 3A.

FIG. 3C schematically illustrates certain images and effects that can bepresented during viewing at an angle in the specular direction by asecurity device in accordance with certain embodiments described herein.

FIG. 3D schematically illustrates certain images and effects that can bepresented during viewing at an angle not in the specular direction by asecurity device in accordance with certain embodiments described herein.

FIGS. 4A, 4B, and 4C schematically illustrate certain images and effectsthat can be presented for viewing by a security device in accordancewith certain embodiments described herein.

FIG. 5A schematically illustrates certain features of an examplesecurity device in accordance with certain embodiments described herein.

FIG. 5B-1 schematically illustrates a top view of a security thread.

FIG. 5B-2 schematically illustrates a side view of the security threadshown in FIG. 5B-1 with a protective coating in accordance with certainembodiments described herein.

FIG. 5C schematically illustrates certain features of another examplesecurity device in accordance with certain embodiments described herein.

FIG. 6A shows the relative brightness as a function of distance of aline scan across an icon (e.g., represented by a number “1”) in anexample security device in accordance with certain embodiments describedherein.

FIGS. 6B-1, 6B-2, 6B-3, and 6B-4 show the relatively high contrast andsharpness of the edges of the icons presented in certain embodiments ofdevices described herein.

FIG. 7 schematically illustrates the change in brightness of two iconsswitching for various angles of tilt in a security device in accordancewith certain embodiments described herein.

FIG. 8A shows certain images (e.g., art objects) and effects that can bepresented for viewing by a security device in accordance with certainembodiments described herein.

FIG. 8B shows an example half-tone pattern in accordance with certainembodiments described herein.

FIG. 8C schematically illustrates an example security device utilizinghalf-tone patterning in accordance with certain embodiments describedherein.

FIG. 9 shows an icon within an icon that switches to a different iconwithin an icon.

FIGS. 10A and 10B schematically illustrate example color generatingstructures including a plasmonic structure.

FIG. 11 schematically illustrates an example color generating structureincluding a reverse opal structure.

FIG. 12 schematically illustrates an example method of forming variouscolor generating structures described herein.

FIGS. 13A and 13B schematically illustrate example devices in accordancewith certain embodiments described herein.

FIG. 14A schematically illustrates an isometric view of an examplesecurity device including a 2D lens array disposed over a plurality ofportions having optical features as described herein. The device can beconfigured to present different distinct images when viewed fromdifferent directions. FIGS. 14B, 14C, 14D, 14E, 14F, 14G, and 14H showtop views of example security devices including a 2D lens array disposedover a plurality of portions having optical features as describedherein.

DETAILED DESCRIPTION

A first line of defense to prevent counterfeiting and the effectivenessof a security system are often by first line inspection, for example, bythe general public. Banknote security features preferably are easilyseen under a variety of light conditions within a 5-10 second time frameand remembered, by the public, including people who are color blind. Inaddition, the security feature in general, should not be able to becopied by electronic or photographic means.

The trend in security features has been toward more complicatedstructures and color changing effects. This trend, however, has beenself-defeating as regards the general public. Such complicated securitydevices have confused the average person looking for a distinctivesecurity feature. On the other hand, there is a high general awarenessby the general public of the banknote watermark (around 70% know of it).The watermark is an image defined by light and dark regions as seen byholding up a banknote to see the watermark in light transmission. Also,color shifting features are low in the public's recognition andawareness. For example, colors in color shifting inks are not bright.Colors in kinegrams are bright, but are too complicated for the averageperson to remember it or to hone in the feature for authenticity. Recentsecurity devices (e.g., color shifting ink and motion type features) arenot readily seen under low light conditions (e.g., at low lit bars,restaurants, etc.), are poor in image definition, or have slow opticalmovement relative to the movement of the banknote.

What is needed in many security devices, therefore, is a sharp imagewith high contrast to the background that switches on and off, orswitches to a different image, at a high rate of change, with little, ifno, transition state, while operating under a variety of lightconditions, including low light. In essence, a high contrast reflective“watermark” that changes its image when one changes its viewing angle bya small angle is desired.

Certain embodiments described herein utilize the dramatic effect ofblack icons that transform themselves to a shiny silver color or to adifferent image against a white diffuse background as the device istilted relative to the observer. Certain embodiments use the gamut ofblack, white, and grey to create intense high definition images.

In accordance with certain embodiments described herein, optical switchdevices, such as security devices are disclosed. Although embodimentsmay be described with respect to security devices, the devices disclosedherein can also be used for non-security devices. In variousembodiments, the security device, when illuminated, can present an iconfor viewing. The icon can appear bright or dark and can appear sharp(e.g., have high definition) against its background. In certainembodiments, upon tilting the device, a user can switch the icon on andoff (and/or switch the icon off and on), and in various instances, atrelatively small tilt angles (e.g., from 2 degrees to 15 degrees in somecases). In various other embodiments, instead of switching an icon onand off upon tilting the device, a user can switch between at least twoicons. Advantageously, the security devices disclosed herein can presentsharp, high contrast icons that switch rapidly, which are difficult tocounterfeit. For additional security, various embodiments of featuresdescribed herein can be combined together and/or with other featuresknown in the art or yet to be developed.

Certain embodiments of security devices described herein can present oneor more sharp icons with high contrast to the background byincorporating two different types of optical features having highcontrast with respect to each other. In some embodiments, the opticalfeatures can include specular reflecting features (e.g., opticallyvariable) and diffusing features (e.g., optically invariable).

In some embodiments, the specular reflecting features and the diffusefeatures can be incorporated into a security device including an arrayof lenses that is configured to switch an icon on and off upon tiltingthe device (e.g., tilting the devices such that the viewer moves his orher observation angle, while the light source remains fixed inposition). In some embodiments, the position of the light source can bemoved while keeping the observer's angle fixed with no change in theshape of the image (e.g., the shape of the image can remain invariant).FIGS. 1A and 1B schematically illustrate an example of such a securitydevice. As shown in FIG. 1A, the security device 100 can include anarray 105 of lenses and a plurality of first segments 101 and secondsegments 102 disposed under the array 105 of lenses. Referring to FIG.1B, a first segment 101 a, 101 b, 101 c, 101 d can correspond to aportion of the icon 112 and/or background 115. Referring to FIG. 1A, ata first viewing angle α (e.g., an angle relative to a normal plane ofthe device 100), the array 105 of lenses can be configured to allow theicon 112 to be viewable. At a second viewing angle β (e.g., an anglerelative to a normal plane of the device 100) different from the firstviewing angle α, the array 105 of lenses can be configured to not allowthe icon 112 to be viewable. For example, the first segments 101 caninclude specular reflecting features and diffusing features, whereas thesecond segments 102 can include either specular reflecting features ordiffusing features as will be disclosed herein. (Or the second segments102 can include specular reflecting features and diffusing features,whereas the first segments 101 can include either specular reflectingfeatures or diffusing features.)

In FIG. 1A, the array 105 of lenses can switch the icon 112 on and offupon tilting the device 100 from the first viewing angle α to the secondviewing angle β. For example, the security device 100 can include a setof first segments 101 and a set of second segments 102 disposed underthe array 105 of lenses. The first segments 101 can correspond toportions of the icon 112 and a first background 115, such that at thefirst viewing angle α, the array 105 of lenses can allow the icon 112and first background 115 to be viewed. The second segments 102 cancorrespond to portions of a second background 125 without an icon 112(e.g., as represented by the absence of the icon 112 within secondbackground 125), such that at the second viewing angle β, the array 105of lenses does not allow the icon 112 to be viewed. Thus, by tilting thedevice 100 from the first viewing angle α to the second viewing angle β,the array 105 of lenses can switch the icon 112 on and off. As such, theviewer can see the icon 112 appear and disappear upon tilting the device100.

In various embodiments, the array 105 of lenses can include a 1-D arrayof lenses. As shown in FIG. 1C-1, the lenses can extend in length muchlonger than shown in FIG. 1A. However, the drawings and schematics aremerely illustrative. A wide variation in sizes and dimensions arepossible. In some embodiments, referring to FIG. 1A, the array 105 oflenses can include a number of cylindrical, hemi-cylindrical lenses,truncated hemi-cylindrical lenses, or plano convex cylindrical lenseswith one convex surface and one plano surface. In some embodiments, thelenses can have one convex surface and one concave surface.

The array of lenses can include a micro lens array having a pitch (e.g.,lateral distance between the centers of two lenses) that can be in arange from 5 microns to 200 microns (such as 6.6 microns, 8.4 microns,12.5 microns, 16 microns, 22 microns, 84 microns, 120 microns, 150microns, etc.), in any ranges within this range (such as 5 microns to150 microns, 5 microns to 100 microns, 5 microns to 85 microns, 5microns to 50 microns, 5 microns to 25 microns, 5 microns to 20 microns,6.6 microns to 150 microns, 6.6 microns to 22 microns, 8.4 microns to150 microns, 8.4 microns to 22 microns, 12.5 microns to 150 microns, 16microns to 150 microns, 22 microns to 150 microns, 84 microns to 150microns, etc.), any values within these ranges, or in any ranges formedby such values. In certain embodiments, the pitch can be constant acrossthe array 105 of lenses. However, in some embodiments, the pitch canvary across the array 105.

A lens within the array 105 of lenses can have a width W_(L) (e.g.,along the x-axis) that can be in a range from 5 microns to 200 microns(such as 6.6 microns, 8.4 microns, 12.5 microns, 16 microns, 22 microns,84 microns, 120 microns, 150 microns, etc.), in any ranges within thisrange (such as 5 microns to 150 microns, 5 microns to 100 microns, 5microns to 85 microns, 5 microns to 50 microns, 5 microns to 25 microns,5 microns to 20 microns, 6.6 microns to 150 microns, 6.6 microns to 22microns, 8.4 microns to 150 microns, 8.4 microns to 22 microns, 12.5microns to 150 microns, 16 microns to 150 microns, 22 microns to 150microns, 84 microns to 150 microns, etc.), any values within theseranges, or in any ranges formed by such values. In certain embodiments,the width W_(L) of a lens can be the same as the width W_(L) of anotherlens in the array 105 of lenses. However, in other embodiments, thewidth W_(L) of a lens can be different than the width W_(L) of anotherlens in the array 105 of lenses.

The radius of curvature of a lens can be in a range from 5 microns to100 microns (such as 5 microns, 12.5 microns, 25 microns, 37.5 microns,50 microns, 62.5 microns, 75 microns, 87.5 microns, 100 microns, etc.),in any ranges within this range (such as 5 microns to 87.5 microns, 5microns to 75 microns, 12.5 microns to 87.5 microns, 12.5 microns to 75microns, etc.), any values within these ranges, or in any ranges formedby such values. In some embodiments, the radius of curvature of a lenscan be different from the radius of curvature of another lens in thearray 105 of lenses. The curvature can be rotationally symmetrical orcan be rotationally asymmetrical.

The lenses can be made of various materials such as a polymer. Forexample, the array 105 of lenses can be UV casted into a resin layercoated on a polymer substrate. Some example substrate materials caninclude, but are not limited to, polyethylene terephthalate (PET),oriented polypropylene (OPP), low density polyethylene (LDPE), linearlow density polyethylene (LLDPE), polypropylene (PP), polyvinyl chloride(PVC), or polycarbonate (PC). As another example, the array 105 oflenses can be molded or embossed in a polymer substrate. Moldable and/orembossable substrates can include acrylonitrile butadiene styrene (ABS),polymethyl methacrylate (PMMA), polyethylene (PE),polycarbonate/acrylonitrile butadiene styrene (PC/ABS), and polyethyleneterephthalate glycol-modified (PETG). Other methods and materials knownin the art or yet to be developed can be used.

In some embodiments, a lens can have a focal length (and correspondingf-number) and be disposed at a distance with respect to the back side ofthe substrate in comparison to the lens's focal length to focus light onthe back side of the substrate. In other embodiments, a lens can have afocal length (and corresponding f-number) and be disposed at a distancewith respect to the back side of the substrate in comparison to thelens's focal length to focus light on the front side of the substrate.In yet other embodiments, a lens can have a focal length (andcorresponding f-number) and be disposed at a distance with respect tothe back side of the substrate in comparison to the lens's focal lengthto focus light in between the front and back sides of the substrate.Example focal lengths include a number that can be in a range from 5microns to 200 microns (such as 5 microns, 12.5 microns, 25 microns,37.5 microns, 50 microns, 62.5 microns, 75 microns, 87.5 microns, 100microns, 112.5 microns, 125 microns, 137.5 microns, 150 microns, 162.5microns, 175 microns, 187.5 microns, 200 microns, etc.), in any rangeswithin this range (such as 5 microns to 187.5 microns, 5 microns to 175microns, 12.5 microns to 187.5 microns, 12.5 microns to 175 microns,etc.), any values within these ranges, or in any ranges formed by suchvalues. In some embodiments, the focal length (and f-number) of a lenscan be different from the focal length (and f-number) of another lens inthe array 105 of lenses.

Although the array 105 of lenses is illustrated in FIG. 1A as a 1D arrayof lenses, in some embodiments, the array 105 of lenses can include a 2Darray of lenses. FIG. 1C-2 shows an example 2D array of lenses. A 1Darray of lenses (e.g., FIG. 1A) can include a series of cylindrical,hemi-cylindrical lenses, truncated hemi-cylindrical lenses, or planoconvex cylindrical lenses in a row with power (e.g., curvature) in onedirection only, whereas a 2D array of lenses (e.g., FIG. 1C-2) can havepower (e.g., curvature) in two directions. In various embodiments, the2D array comprises lenses having surfaces that are rotationallysymmetric surfaces. In some embodiments, the 2D array can compriselenses having surfaces that are asymmetrical. For example, the lensescan be elliptical in that the lenses are longer in one orthogonaldirection compared to the other. In some embodiments, the 2D array cancomprise spherical lenses. In some embodiments, the 2D array cancomprise lenses with aspheric surfaces. In various embodiments, the 2Darray can comprise elliptical, hexagonal, Fresnel and/or achromaticlenses. The lenses in the 2D lens array can be arranged in close packedarrangement or in a square arrangement. The shape and or arrangement ofthe lenses, however, should not be considered to be limited. Asadditional examples, the surfaces of the lenses can be convex,aspherical, toroidal, and/or de-centered. The lenses may have circular,square, rectangular, hexagonal aperture shape or footprint, or may haveother shapes, and the aperture may be truncated. Similarly, the lensesmay be arranged in a square array, triangular array, hexagonal closedpacked, or arranged otherwise. In some embodiments, the array 105 oflenses can include a first lenticular lens array having a firstlongitudinal axis and a second lenticular lens array having a secondlongitudinal axis. In some instances, the first and second arrays can bearranged such that the first longitudinal axis of the first array can beangled from 5 to 90 degrees (or any range within this range, such asfrom 5 to 80 degrees, 10 to 90 degrees, 20 to 90 degrees, etc.) withrespect to the second longitudinal axis of the second array.

In various embodiments, the array 105 of lenses can include a series oflenses (e.g., lenticular lenses, microlenses, spherical lenses, etc.)configured to allow the features disposed under the lenses correspondingto different images to be viewable at different viewing angles. Forexample, in some cases, the lenses are magnifying lenses to enlargedifferent features disposed under the lenses corresponding to differentimages at different viewing angles. As another example, the lenses canprovide an avenue to switch between different images through differentchannels. Thus, the security device 100 can include a set of firstsegments 101 and a set of second segments 102 disposed under the array105 of lenses.

In FIG. 1B, the first segments 101 and the second segments 102 areinterlaced with each other. A first segment 101 a, 101 b, 101 c, 101 dcan correspond to a portion of a first image 110 (only top portionillustrated), such that at the first viewing angle α, the array 105 oflenses can be configured to allow the plurality of portions of the firstimage 110 to be viewable. Although the array 105 of lenses allows aplurality of separate portions to be viewable, the viewer can see thesum total of all the portions of the first image 110 (e.g., the wholefirst image 110). A second segment 102 a, 102 b, 102 c, 102 d cancorrespond to a portion of a second image 120, such that at the secondviewing angle β, the array 105 of lenses can be configured to allow theplurality of portions of the second image 120 to be viewable. Althoughthe array 105 of lenses allows a plurality of separate portions to beviewable, the viewer can see the sum total of all the portions of thesecond image 120 (e.g., the whole second image 120).

In the example shown in FIGS. 1A and 1B, the first image 110 includes anicon 112 and a first background 115, whereas the second image 120includes a second background 125 without an icon 112. In variousembodiments, the first image 110 (or icon 112) can include at least onealphanumeric character, a symbol, an image (e.g., an art image), a halftone image, graphic, or an object. Other items are possible. In thisexample, the first image 110 shown is an icon 112 of the letter A.

Since the first image 110 includes icon 112, the array 105 of lensesallows the icon 112 to be viewable at the first viewing angle α.However, since the second image 120 does not include the icon 112, thearray 105 of lenses does not allow the icon 112 to be viewable at thesecond viewing angle β. Thus, by tilting the device 100 from the firstviewing angle α to the second viewing angle β, the array 105 of lensescan switch the icon 112 on and off.

Referring to FIG. 1A, the first segments 101 and the second segments 102can be disposed under the array 105 of lenses. In various embodiments,the first segments 101 and the second segments 102 can have a width wsmaller than the width W_(L) of a lens in the array 105 of lenses. Insome embodiments, a pair of a first segment 101 and a second segment 102can be aligned under each lens in the array 105 of lenses. However, apair of a first segment 101 and a second segment 102 need not be exactlyaligned under a single lens in the array 105, but might be offset fromsuch an alignment. For example, a first segment 101 can be disposedunder a single lens in the array, while a portion of a second segment102 can be disposed under parts of two different lenses in the array105. Thus, in various embodiments, the pairs of a first segment 101 anda second segment 102 under the array 105 of lenses are not alignmentsensitive (e.g., exact alignment of pairs of a first segment 101 and asecond segment 102 under a single lens in the array 105 is notnecessary).

Although exact alignment of the pairs of a first segment 101 and asecond segment 102 under a single lens in the array 105 is notnecessary, a lens within the array 105 of lenses can be registered onaverage to a pair of a first segment 101 and a second segment 102. Forexample, a lens can correspond to a pair of a first segment 101 and asecond segment 102. Light from a first segment 101 can pass through afirst part of a lens and light from a second segment 102 can passthrough a separate part of the lens, and corresponding portions of thelens can form the distinct images at two different angles as describedherein. On average, most of the lens may be registered with respect tothe segments 101, 102 in this manner.

A first segment 101 and/or a second segment 102 can have a length l(along the y-axis), width w (along the x-axis), and thickness t (alongthe z-axis). The length l, width w, and thickness t are not particularlylimited, and can be based on the application. In some embodiments, thewidth w of a first segment 101 and/or a second segment 102 can be basedon the size of the lenses in the array 105 (e.g., approximately half ofthe pitch of the lens). In various embodiments, for example, for asecurity thread on a banknote, the width w of a first 101 and/or asecond 102 segment can be less than or equal to 80 microns, less than orequal to 70 microns, or less than or equal to 60 microns, and/or in arange from 10 microns to 80 microns, in any range within this range(e.g., 10 microns to 75 microns, 15 microns to 75 microns, 15 microns to70 microns, etc.), any values within these ranges, or in any rangesformed by such values. A first segment 101 and/or the second segments102 can include multiple features per segment. For example, the featurescan include less than 10 micron sized features (as will be describedherein) which correspond to portions of an image. In variousembodiments, the array 105 of lenses can magnify the less than 10 micronsized features disposed under the lenses to be viewable with theun-aided eye. For example, in some embodiments, the first segment 101and/or the second segment 102 may have a width w that is about half thewidth W_(L) of a lens. When viewing the first 101 and/or second 102segment under a lens in the array 105, however, the features may fillthe width of the lens and thus the features within the segment mayappear the size of the full width of the lens or at least larger thanthe segment itself. In certain embodiments, the first segment 101 and/orthe second segment 102 can include a micro-image (e.g., at least onealphanumeric character, symbol, an art image, graphic, an object, etc.)not viewable by the un-aided eye where the height of the micro-image issmaller than the width w of the segment 101, 102. In some suchembodiments, the array 105 of lenses can magnify the micro-image suchthat it is viewable by the un-aided eye. In other such embodiments, foran additional security feature, the micro-image can remain un-viewableby the un-aided eye but viewable with an additional aid such as amagnifying glass or microscope.

In various embodiments, the array 105 of lenses can be disposed on afirst side 151 of a substrate or carrier 150. The first segments 101 andthe second segments 102 can be disposed on the second side 152 oppositethe first side 151 of the substrate 150. Referring to FIG. 1B, someembodiments can be manufactured by applying the specular reflectingfeatures 132 and/or applying the diffusing features 135, 145 onto thesubstrate or carrier 150, e.g., on the second side 152 of the substrate150. In some embodiments, the specular reflecting features 132 and thediffusing features 135 can be embossed into a coating or the substrateor carrier 150. After UV curing the embossed coating or substrate, thespecular reflecting features 132 and the diffusing features 135 can bemetallized (e.g., at the same time in some cases). The substrate orcarrier 150 can comprise various polymeric substrates, such as, forexample, polyethylene terephthalate (PET), oriented polypropylene (OPP),low density polyethylene (LDPE), linear low density polyethylene(LLDPE), polypropylene (PP), polyvinyl chloride (PVC), polycarbonate(PC) or any other type of plastic film or carrier. In variousembodiments, the polymeric substrate can be transparent. The polymericsubstrates can have a thickness that can be in a range from 10 micronsto 300 microns (e.g., 12.5 microns, 25 microns, 37.5 microns, 50microns, etc.), in any range within this range (e.g., 10 microns to 200microns, 12.5 microns to 100 microns, 12.5 microns to 50 microns, etc.),any values within these ranges, or in any ranges formed by such values.

After the device 100 is formed, some such devices 100 can beincorporated into a banknote having a paper, plastic, or polymericthickness that can be in a range from 10 microns to 110 microns (e.g.,12.5 microns, 25 microns, 40 microns, 50 microns, 90 microns, 95microns, 98 microns, 100 microns, 105 microns, 107 microns, etc.), inany range within this range (e.g., 10 microns to 105 microns, 10 micronsto 90 microns, 10 microns to 50 microns, 10 microns to 40 microns,etc.), any values within these ranges, or in any ranges formed by suchvalues. In some embodiments, various devices 100 can be incorporatedinto a banknote (e.g., embedded into or laminated onto the paper,plastic, or polymer of the banknote) such that the total banknotethickness can be in a range from 10 microns to 130 microns, from 10microns to 120 microns, from 10 microns to 110 microns, from 10 micronsto 100 microns, from 10 microns to 90 microns, in any range within theseranges, any values within these ranges, or in any ranges formed by suchvalues. The security device 100 can be formed into security threads inbanknotes. A security thread can be a polymeric film interwoven into thebanknote paper (or plastic or polymer) as it is being made such thatportions of it are visible at the surface and some portions are not. Thesecurity device 100 can be a hot stamp feature, an embedded feature, awindowed feature, or a laminated feature. A hot stamp feature can betransferred to a banknote surface using a release substrate upon whichmay be located a security feature, e.g., a hologram, using heated dieand pressure. A patch is generally hot stamped to a banknote surface. Anembedded feature can be affixed within a depression, e.g., formed duringthe paper (or plastic or polymer) making process, in the banknote. Insome embodiments, this feature can keep the banknote surface flat. Awindowed feature can allow one to view the security device intransmission. A windowed feature can include an opening in the banknotepaper (or plastic or polymer) and can be laminated with a polymericfilm. A windowed feature can include a security thread interwoven intothe banknote paper (or plastic or polymer). A laminated feature can beaffixed to the surface of the banknote by means of an adhesive. Alaminated strip can include a flat polymer film with built in opticalsecurity devices. This flat polymer film can be attached to a banknoteacross its width (e.g., narrow dimension) using adhesive on the banknotesurface. In some embodiments, the security device 100 can be configuredto provide authenticity verification on an item of security (e.g.,currency, a credit card, a debit card, a passport, a driver's license,an identification card, a document, a tamper evident container orpackaging, or a bottle of pharmaceuticals).

Although FIGS. 1A and 1B show two sets of segments (e.g., first segments101 and second segments 102), additional sets of segments (e.g., thirdsegments, fourth segments, etc.) can be included. For the same sizedarray 105 of lenses, to incorporate additional segments, the width w ofthe segments may be reduced. Alternatively, to incorporate additional(e.g., same sized) segments, the size of the lenses (e.g., W_(L)) may beincreased.

With further reference to FIG. 1B, the first segments 101 can includespecular reflecting features 132 and diffusing features 135. Thespecular reflecting features 132 can define the icon 112 and thediffusing features 135 can define the first background 115. In variousembodiments, a master used to form the specular reflecting features 132and/or the diffusing features 135 can be prepared by using an electronbeam, lithographic techniques, and/or etching.

The specular reflecting features 132 can be provided by a mirror such asa metallized relatively flat and/or smooth surface. In some instances,the metallized surface can include metals such as aluminum, silver,gold, copper, titanium, zinc, tin, and alloys thereof (e.g., bronze).

The diffusing features 135 can be provided by a diffuser such as akinoform diffuser (and may be replicated from a master that was formedusing a holographic process that involved interfering light on aphotosensitive material), a tailored micro diffuser, or a resincontaining scattering particles such as TiO₂ or other type of diffuser.In certain embodiments, the diffusing features 135 can provide a mattewhite or a paper white finish or a grey finish. The surface texture ofthe diffusing features 135 can provide “color consistency” (e.g., aconsistent white or grey look). In various embodiments, the surfacetexture of the specular reflecting features 132 can provide “colorcontrast” with the diffusing features 135 (e.g., providing a dark orshiny look adjacent the white or grey look). In some embodiments, thediffusing features 135 can include a tint, dye, ink, or pigment (orother material where absorption provides color) to change the color fromwhite or grey, but maintain a matte finish appearance (e.g. a mattecolor such as matte green, matte red, etc.). In various embodiments, thehigh contrast and consistency can allow the presented image to berelatively invariant as the light source changes its position. An imagehaving high contrast and consistency is effective in public recognitionand awareness, which can be advantageous for a security device.

In various embodiments, the diffusing features 135 can includerelatively fine and shallow features allowing the features to be used ona product (e.g., a bank note) without substantially increasing thethickness of the product. Further, a smaller sized feature in general,allows more features to be incorporated for a line of an image, whichcan allow for better diffusion and increase the resolution of the image.

The surface measurements of the diffusing features 135 can be measuredby various instruments, such as by an apparatus marketed by Keyence. Forexample, the surface texture can be analyzed based on InternationalStandard ISO 25178 to measure, for example, arithmetic mean height,maximum height, texture aspect ratio, arithmetic mean peak curvature,developed interfacial area ratio, root mean square height, skewness,kurtosis, maximum peak height. An example diffuser was measured withinthe following parameters. The diffusing features 135 can have anarithmetic mean height Sa (e.g., arithmetic mean of the absolute valueof the height from the mean plane of the surface) less than or equal to5 microns (e.g., less than or equal to 1 micron, less than or equal to0.5 micron, less than or equal to 0.3 micron, less than or equal to 0.2micron, etc.), and/or have an arithmetic mean height from 0.01 micron to5 microns, in any range within this range (e.g., 0.01 micron to 3microns, 0.01 micron to 1 micron, 0.01 micron to 0.5 micron, 0.05 micronto 3 microns, 0.05 micron to 1 micron, 0.05 micron to 0.5 micron, 0.05micron to 0.3 micron, 0.05 micron to 0.2 micron, 0.1 micron to 1 micron,0.1 micron to 0.5 micron, 0.1 micron to 0.3 micron, 0.1 micron to 0.2micron, etc.), of any values within these ranges, or in any rangesformed by such values. In certain embodiments, the maximum height Sz(e.g., distance between the highest point and the lowest point on thesurface) of the diffusing features 135 can be less than or equal to 10microns (e.g., less than or equal to 8 microns, less than or equal to 5microns, less than or equal to 3 microns, less than or equal to 2microns, etc.) and/or be from 0.01 micron to 10 microns, in any rangewithin this range (e.g., 0.1 micron to 5 microns, 0.15 micron to 5microns, 0.2 microns to 5 micron, 0.5 micron to 5 microns, 0.5 micron to3 microns, 1 micron to 3 microns, etc.), any values within these ranges,or in any ranges formed by such values. The diffusing features 135 canhave a texture aspect ratio Str (e.g., a measure of uniformity of thesurface texture) of less than 5 (e.g., less than 3, less than 1, etc.),and/or have a texture aspect ratio from 0.01 to 5, in any range withinthis range (e.g., from 0.2 to 1, from 0.5 to 1, etc.), of any valueswithin these ranges, or in any ranges formed by such values. In someembodiments the diffusing features 135 can have an arithmetic mean peakcurvature Spc (e.g., the arithmetic mean of principal curvature ofpeaks) greater than or equal to 1,000 l/mm (e.g., greater than or equalto 10,000 l/mm, greater than or equal to 30,000 l/mm, etc.), and/or havean arithmetic mean peak curvature from 1,000 l/mm to 100,000 l/mm, inany range within this range (e.g., 10,000 l/mm to 80,000 l/mm, 15,000l/mm to 80,000 l/mm, 25,000 l/mm to 65,000 l/mm, 30,000 l/mm to 50,000l/mm, etc.), of any values within these ranges, or in any ranges formedby such values.

In various examples, the developed interfacial area ratio Sdr (e.g.,percentage of the definition area's additional surface area contributedby the texture as compared to the planar footprint or definition area)of the diffusing features 135 can be less than or equal to 10 (e.g.,less than or equal to 5, less than or equal to 4, less than or equal to3, less than or equal to 2, etc.), and/or have a developed interfacialarea ratio from 0.5 to 10, in any range within this range (e.g., from0.8 to 7, from 1 to 2, from 1.2 to 1.8, etc.), of any values withinthese ranges, or in any ranges formed by such values. In someembodiments, the root mean square height Sq (e.g., standard deviation σof heights) can be less than or equal to 5 microns (e.g., less than orequal to 0.5 micron, less than or equal to 0.3 micron, less than orequal to 0.2 micron, etc.), and/or have a root mean square height from0.05 micron to 5 microns, in any range within this range (e.g., 0.05micron to 1 micron, 0.05 micron to 0.5 micron, 0.1 micron to 0.5 micron,etc.), of any values within these ranges, or in any ranges formed bysuch values. The diffusing features 135 can have skewness Ssk (e.g.,degree of bias of the roughness shape) of less than or equal to 5 (e.g.,less than or equal to 3, less than or equal to 1, etc.), and/or have askewness from 0.01 to 5, in any range within this range (e.g., from 0.5to 5, from 0.6 to 2, from 0.7 to 1, etc.), of any values within theseranges, or in any ranges formed by such values. The surface can have akurtosis Sku (e.g., measure of the sharpness of the roughness profile)of less than or equal to 10 (e.g., less than or equal to 8, less than orequal to 5, etc.), and/or have a kurtosis from 0.5 to 10, in any rangewithin this range (e.g., from 0.8 to 9, from 1.2 to 7, from 2 to 5,etc.), of any values within these ranges, or in any ranges formed bysuch values. The maximum peak height Sp (e.g., height of the highestpeak) of the diffusing features 135 can be less than or equal to 10microns (e.g., less than or equal to 8 microns, less than or equal to 5microns, less than or equal to 3 microns, less than or equal to 2microns, etc.) and/or be from 0.05 micron to 10 microns, in any rangewithin this range (e.g., 0.1 micron to 5 microns, 0.15 micron to 3microns, 0.18 micron to 2 microns, etc.), any values within theseranges, or in any ranges formed by such values.

The diffusing features 135 can be configured to provide Lambertianreflectance, such as reflectance with the brightness appearing the sameregardless of one's angle of view. In some instances, the diffusingfeatures 135 can have an elliptical or linear output. In variousembodiments, the diffusing features 135 can be characterized by aBi-Directional Reflectance Distribution Function (BRDF), and can have azero-order peak. In some embodiments, the diffusing features 135 canhave a brightness greater than or equal to 85, such as 85, 86, 88, 90,95, 99 and/or in a range from 85 to 100, in any range within this range(e.g., from 88 to 100, from 90 to 100, etc.), of any values within theseranges, or in any ranges formed by such values and/or can have awhiteness index greater than or equal to 85, such as 85, 86, 88, 90, 95,99 and/or in a range from 85 to 100, in any range within this range(e.g., from 88 to 100, from 90 to 100, etc.), of any values within theseranges, or in any ranges formed by such values. In various embodiments,the device can be dependent on the color of the light source. Forexample, if one views the device under a sodium light source, theoverall color can be yellowish, whereas under a white light source, thedevice can be achromatic (without color).

In certain embodiments, because of a relatively high contrast betweenthe specular reflecting features 132 and the diffusing features 135 aswill be disclosed herein, the security device 100 can operate under avariety of light sources, including low light (e.g., subdued lighting asfound in bars and restaurants or at dusk or at dawn). In certainembodiments, the specular reflecting features 132 and the diffusingfeatures 135 can provide no diffractive or interference color (e.g., nowavelength dispersion or rainbows or rainbow effects). In variousembodiments, the range of brightness from white to black can be used,without color (e.g., achromatic). However, some embodiments can becolored (e.g., green, red, brown, yellow, etc.) so that a monochromaticeffect can be seen. For example, in some embodiments, the diffusingfeatures can comprise a tint, an ink, a transparent dye, an opaque dye,or an opaque pigment where absorption can provide color.

By incorporating specular reflecting features 132 to define the icon 112and diffusing features 135 to define the first background 115 of thefirst image 110, certain embodiments of security devices 100 can presentrelatively high contrast between icon 112 and first background 115 and asharp border between the icon 112 and first background 115. One way tocharacterize the border or a high definition line can be by thedifferential (e.g., derivative or slope) across the boundary. Relativelysharp lines with little or no gradual change or having a ragged edge cantypically have a rapidly changing profile. Those that have a gradualtransition from one brightness to another brightness can have a slowrising and receding differential trace. Relatively high contrast canhave a narrow differential trace with large height while relatively lowcontrast can have a wide differential trace with small height. Invarious embodiments, a 3D profile of the surface can be mapped, e.g.,with a ZYGO interferometer, between a region including specularreflecting features 132 and a region including diffusing features. Insome embodiments, the width of the physical transition of the boundarycan be from 0.1 micron to 2 microns (e.g., 0.8 micron, 1 micron, 1.2microns, etc.), in any range within this range (e.g., 0.2 micron to 2microns, 0.5 micron to 2 microns, etc.), any values within these ranges,or in any ranges formed by such values.

Various discussions provided herein refer to viewing in the speculardirection (e.g., on-axis viewing) as well as viewing in a directionother than the specular direction (e.g., off-axis viewing). As is wellknown, according to Snell's law, light incident on a flat smooth surfaceat an angle of incidence, θ_(i), (e.g., measured with respect to thesurface normal of the flat smooth surface) will be reflected at an angleof reflection, θ_(r), (e.g., measured with respect to the surface normalof the flat smooth surface) such that the angle of incidence, θ_(i), isequal to the angle of reflection, θ_(r), (e.g., θ_(i)=θ_(r)). Thespecular direction refers to the direction of this reflected light,e.g., the reflected light directed at the angle, θ_(r), with respect tothe normal. The direction other than the specular direction refers tothe direction not corresponding to the direction of this reflectedlight, e.g., the reflected light directed at the angle, θ_(r), withrespect to the normal off the surface. The specular direction is alsoused herein in connection with diffuse surfaces to correspond to theangle of reflection, θ_(r), that is equal to the angle of incidence,θ_(i), even though a diffuse surface will not necessarily limit thelight scattered therefrom to the specular direction and will scatterlight in many directions other than in a directions having an angle ofreflection, θ_(r), equal to the angle of incidence, θ_(i). The terms“on-axis” and “off-axis” may also be used interchangeably with thedirection of specular reflection and a direction not corresponding tothe specular direction, respectively. Although the description aboverefers to the angles of reflection as is applicable for reflectivesurfaces, the structures described herein should not be limited toreflective structures and may, for example, comprise transmissivestructures and/or a combination of reflective and transmissivestructures. For example, instead of metallized specular reflectingfeatures 132 and the diffusing features 135 reflecting light from thesame side of the array 105 of lenses, the features 132, 135 may allowlight to transmit through from the opposite side of the array 105 oflenses. In various embodiments, a coating of partially transmissive andpartially reflective ZnS or other high refractive index material can bedeposited over the microstructure of the specular reflecting features132 and the diffusing features 135 followed by an opaque coating ofvacuum deposited aluminum. The aluminum can be selectively metallized(e.g., using a partial metallization method such as forming a patternedmetal layer using an oil ablation technique) or demetallized (e.g.,using a demetallization method such as alkali etching to remove exposed,unprotected metal) such that the regions having specular reflectingfeatures 132 are reflective and diffusing features are transmissive.Alternatively, in some embodiments, only a high index coating coversboth the specular reflecting features 132 and diffusing features 135such that both features are viewed in transmission. After the device iscoupled (e.g., laminated) to the backside 152 of the substrate orcarrier 150, the ZnS layer can provide a high index layer. For example,the index mismatch can provide reflection (e.g., Fresnel reflection).Alternatively, in some embodiments, the high index layer can bedeposited after incorporating the aluminum (e.g., after selectivemetallization or after demetallization).

FIG. 2A schematically illustrates viewing at an angle in the speculardirection of specular reflecting features 132 (e.g., on-axis viewing)and at the same angle (e.g., off-axis viewing) of diffusing features 135in accordance with certain embodiments described herein. For simplicity,the array 105 of lenses is not shown. As shown in FIG. 2A, light from anincoming direction I_(S) can be reflected from the specular reflectingfeatures 132 primarily in a single direction R_(S). The reflectance fromthe specular reflecting features 132 can appear the brightest whenviewing in the single direction R_(S) of specular reflectance (e.g.,viewing at an angle in the specular direction).

In contrast, light from an incoming direction I_(D) can be reflectedfrom the diffusing features 135 in multiple directions R_(D). Thereflectance from the diffusing features 135 is generally the same in themultiple directions including in the direction of specular reflectanceof the specular reflecting features 132. In general, the reflectancefrom the diffusing features 135 is not as bright as the reflectance fromthe specular reflecting features 132 when viewing at the angle in thespecular direction. However, the reflectance from the diffusing features135 can be more reflective than the specular reflecting features 132when viewing at an angle not in the specular direction.

For example, as shown in FIG. 2B, because light from an incomingdirection I_(S) can be reflected from the specular reflecting features132 primarily in a single direction R_(S1), the reflectance from thespecular reflecting features 132 can appear dark when viewing at anangle not in the specular direction (e.g., directions R_(S2) other thanthe single direction R_(S1)). With further reference to FIG. 2B, lightfrom an incoming direction I_(D) can be reflected from the diffusingfeatures 135 in multiple directions R_(D). The reflectance from thediffusing features 135 can appear the same (e.g., and not as bright asfrom the specular reflecting features 135 at the specular reflectiveangle) in the multiple directions, e.g., directions of specularreflectance of the specular reflecting features 132 as well as otherdirections.

In certain embodiments, high contrast between two regions (a firstregion defined by the specular reflecting features 132 and a secondregion defined by the diffusing features 135) can be achieved undermultiple, if not all, angles of viewing. For example, FIG. 2Cschematically illustrates certain images and effects that can bepresented during viewing at an angle in the specular direction by asecurity device in accordance with certain embodiments described herein.FIG. 2D schematically illustrates certain images and effects that can bepresented during viewing at an angle not in the specular direction bythe security device in accordance with certain embodiments describedherein. In this example, the specular reflecting features 132 define theicon 112, and the diffusing features 135 define the background 115.Referring to FIG. 2C, the icon 112 appears very bright (e.g., highreflectance) against a matte white or grey background 115. Referring toFIG. 2D, the icon 112 appears dark (e.g., low reflectance) against amatte white or grey background 115. In both viewing situations, there ishigh contrast between the icon 112 and the background 115. The contrastcan be measured as the percentage of the difference between the maximumbrightness and the minimum brightness divided by the sum of the maximumbrightness and minimum brightness. In various embodiments, when viewingat an angle in the specular direction of the specular reflectingfeatures 132 (e.g., FIG. 2C), the contrast of an image presented bycertain devices described herein can be from 25% to 50% (e.g., 30%, 32%,35%, 40%, 42%, 45%, etc.), and/or in any range within this range (e.g.,from 30% to 50%, from 30% to 48%, from 30% to 45%, etc.), any valueswithin these ranges, or in any ranges formed by such values. Whenviewing at an angle not in the specular direction (e.g., FIG. 2D), thecontrast of an image presented by certain devices described herein canbe from 50% to 90% (e.g., 60%, 62%, 65%, 70%, 72%, 75%, 78%, etc.),and/or in any range within this range (e.g., from 55% to 85%, from 60%to 85%, from 60% to 80%, etc.), any values within these ranges, or inany ranges formed by such values. In other embodiments, when viewing atan angle in the specular direction of the specular reflecting features132, the contrast of an image presented by certain devices describedherein can be from 50% to 90% (e.g., 60%, 62%, 65%, 70%, 72%, 75%, 78%,etc.), and/or in any range within this range (e.g., from 55% to 85%,from 60% to 85%, from 60% to 80%, etc.), any values within these ranges,or in any ranges formed by such values. When viewing at an angle not inthe specular direction, the contrast of an image presented by certaindevices described herein can be from 25% to 50% (e.g., 30%, 32%, 35%,40%, 42%, 45%, etc.), and/or in any range within this range (e.g., from30% to 50%, from 30% to 48%, from 30% to 45%, etc.), any values withinthese ranges, or in any ranges formed by such values. In these examples,the contrast percentage is higher for either viewing at an angle in thespecular direction or not in the specular direction. However, in someembodiments, the contrast percentage can be similar for viewing at anangle in the specular direction and not in the specular direction. Forexample, the contrast percentage can be from 25% to 90% (e.g., 30%, 32%,35%, 40%, 42%, 45%, 50%, 60%, 62%, 65%, 70%, 72%, 75%, 78%, etc.),and/or in any range within this range (e.g., from 30% to 50%, from 30%to 48%, from 30% to 45%, from 55% to 85%, from 60% to 85%, from 60% to80%, etc.), any values within these ranges, or in any ranges formed bysuch values for both viewing situations.

In various embodiments, the device 100 can have viewing angles fromnegative angles (e.g., device 100 tilted towards the viewer) through thenormal and to positive angles (e.g., device 100 tilted away from theviewer). Because light from an incoming direction I_(D) can be reflectedfrom the specular reflecting features 132 primarily in a singledirection R_(S1), the device 100 may be viewed at an angle not in thespecular direction for the majority of the time. For example, as thedevice 100 is tilted from negative through the normal and to positiveangles, a dark icon 112 against a matte white or grey background 115(e.g., FIG. 2D) can switch between appearing and disappearing. The icon112 and the backgrounds 115, 125 are achromatic. As the device 100 istilted to the angle of specular reflectance, a very bright icon 112against a matte white or grey background 115 (e.g., FIG. 2C) can appear.In some cases, depending on the metallization and processing of thespecular reflecting features 132, a color (e.g., a shiny aluminum coloror a shiny copper color) may appear momentarily against a matte white orgrey background 115. As the device 100 is tilted out of the angle ofspecular reflectance and beyond, a dark icon 112 against a matte whiteor grey background 115 (e.g., FIG. 2D) can once again switch betweenappearing and disappearing.

Various embodiments can utilize a relatively high contrast and a sharpborder between the two regions, e.g., between the icon 112 and the firstbackground 115, and/or between a region at the first viewing angle α anda region at the second viewing angle (3, e.g., between the icon 112 andthe second background 125. The contrast and sharpness of images in anexample device is shown in FIGS. 6A, 6B-1, 6B-2, 6B-3, and 6B-4.

With reference back to FIG. 1B, the specular reflecting features 132 candefine the icon 112 and the diffusing features 135 can define the firstbackground 115. In other embodiments still utilizing a relatively highcontrast, the specular reflecting features 132 can define the firstbackground 115 and the diffusing features 135 can define the icon 112.As shown in FIG. 1B, the first background 115 can have an outer shape115 b and size. The second background 125 can also have an outer shape125 b and a size. The outer shapes 115 b, 125 b can be shaped asdescribed herein, but are shown in FIG. 1B as a rectangle forsimplicity.

With further reference to FIG. 1B, the second segments 102 can includediffusing features 145. The diffusing features 145 can define the secondbackground 125. Because there is no icon 112 within the secondbackground 125, by tilting the device 100 from the first viewing angle αto the second viewing angle (3, the array 105 of lenses can switch theicon 112 off. In certain embodiments, the diffusing features 145 of thesecond segments 102 can be different than the diffusing features 135 ofthe first segments 101. However, in various embodiments, the diffusingfeatures 145 of the second segments 102 can be the same as the diffusingfeatures 135 of the first segments 101. In some such embodiments (e.g.,with the first and second backgrounds 115, 125 also having the sameouter shape 115 b, 125 b and size), the second background 125 at thesecond viewing angle β looks the same (e.g., in shape, size, andbrightness) as the first background 115 viewable at the first viewingangle α. For example, the viewer can see the icon 112 appear anddisappear against similar backgrounds 115, 125 upon tilting the device100 from the first viewing angle α to the second viewing angle β.Although the array 105 of lenses switches from first background 115 tosecond background 125, the viewer sees a background 125 that appearsunchanged.

In various embodiments, the icon 112 and/or the backgrounds 115, 125 areachromatic. In some instances, the icon 112 and/or the backgrounds 115,125 may be provided with monochromatic color (e.g., green, red, brown,yellow, etc.) by incorporating color to the specular reflecting features132, the diffusing features 135, 145, and/or the lenses in the array 105of lenses, and/or the substrate 150. This may be a matte (or diffuse)color or a mixture of matte colors as well as patterns or images formedby different colors. In some instances, the specular reflecting features132, the diffusing features 135, 145, and/or the array 105 of lenses caninclude a tint, a dye, ink, or a pigment. For an additional securityfeature, the specular reflecting features 132, the diffusing features135, 145, and/or the array 105 of lenses can include a covert feature,such as a fluorescent material (e.g., to emit a color when exposed to UVlight) or an up-converting pigment (e.g., to convert near infrared lightto visible light).

In FIGS. 1A and 1B, the outer shape 115 b of the first background 115 isillustrated as a rectangle. The outer shape 125 b of the secondbackground 125 is also illustrated as a rectangle. As described herein,in some embodiments, the second background 125 can have the same shape,size, and diffusing features 145 as the first background 115 such thatthe background appears unchanged (e.g., in shape, size, and brightness)when tilting the device from a first viewing angle α to a second viewingangle β. In various embodiments, at the first viewing angle α, the array105 of lenses can allow the icon 112 and a shaped background 115 to beobserved. At the second viewing angle β, the array 105 of lenses canallow the same shaped background 125 to be observed. The shape of thebackgrounds 115, 125 is not particularly limited. In some embodiments,the shape can include a pattern of alphanumeric characters, symbols,images (e.g., art images), graphics, or objects. For example, thebackground 115, 125 can include a circle, a square, a rectangle, ahexagon, an oval, a star, or a knurled edge. Other example backgrounds115, 125 can be in the form of a bell, an inkwell, or a number. However,a wide range of other backgrounds are possible. In other embodiments,the shape and/or size of first background 115 and second background 125can be different such that the background may appear to change whentilting the device from a first viewing angle α to a second viewingangle β.

In FIG. 1B, the first segments 101 include specular reflecting features132 defining the icon 112 and diffusing features 135 defining the firstbackground 115, and the second segments 102 include diffusing features145 to match the diffusing features 135 defining the first background115 of the first segments 101. However, in other embodiments, the firstsegments 101 can include diffusing features 135 defining the icon 112and specular reflecting features 132 defining the first background 115,and the second segments 102 can include specular reflecting features 145to match the specular reflecting features 132 of the first segments 101.

As shown in FIGS. 2A and 2B, there is a relatively narrow range ofspecular reflection for the specular reflecting features 132 and arelatively wide range of low reflection. Certain embodiments canincorporate specular reflecting features 132 (e.g., in a first segment101) adjacent to diffusing features 145 (e.g., in a second segment 102)such that the security device 100 can switch an icon 112 on and off withrelatively small tilt angles. For example, under a point light source(e.g., an LED), a user can switch the icon on (or off) upon tilting thedevice, forward or backward, by less than or equal to 15 degrees (e.g.,4 degrees, 5 degrees, 5.5 degrees, 6 degrees, 7 degrees, etc.), and/or arange from 2 degrees to 15 degrees, any range within this range (e.g., 3degrees to 15 degrees, 3 degrees to 14 degrees, 4 degrees to 15 degrees,4 degrees to 14 degrees, 4 degrees to 13 degrees, 5 degrees to 15degrees, 5 degrees to 13 degrees, etc.), any values within these ranges,or any ranges formed by such values. As another example, under anextended light source (e.g., incandescent light), a user can switch theicon on (or off) upon tilting the device, forward or backward, by lessthan or equal to 20 degrees (e.g., 8 degrees, 9 degrees, 10 degrees, 11degrees, etc.), and/or a range from 2 degrees to 20 degrees, any rangewithin this range (e.g., 2 degrees to 18 degrees, 2 degrees to 15degrees, 3 degrees to 15 degrees, 4 degrees to 15 degrees, 5 degrees to15 degrees, 5 degrees to 12 degrees, etc.), any values within theseranges, or any ranges formed by such values.

In some embodiments, the user can switch the icon back off (or back on)upon tilting of the device in the opposite direction by at least thesame tilt angles described herein, or upon further tilting of the devicein the same direction by at least the same tilt angles described herein.Further, incorporating specular reflecting features 132 in a firstsegment 101 adjacent to diffusing features 145 in a second segment 102can provide the relatively high contrast between these regions asdescribed herein. Such incorporation can allow the security device 100to switch an icon 112 on and off with sharp boundaries upon tilting fromviewing angle α to viewing angle β. Advantageously, security devices inaccordance with certain embodiments can present sharp icons that switchon and off rapidly with little, if no, transitional state, which aredifficult to reproduce.

In accordance with certain embodiments described herein, instead ofswitching an icon on and off, a security device can be configured toswitch between at least two icons upon tilting the device. FIGS. 3A and3B schematically illustrate an example of such a security device. Theembodiment shown in FIGS. 3A and 3B is similar to the embodiment shownin FIGS. 1A and 1B except that instead of the second image 120 includingonly the second background 125 (and no second icon), the second image320 in FIGS. 3A and 3B includes a second icon 322 in addition to thesecond background 325. Accordingly, the features disclosed hereinrelating to the embodiment shown in FIGS. 1A and 1B extend to theembodiment shown in FIGS. 3A and 3B.

For example, as shown in FIG. 3A, the security device 300 can include anarray 305 of lenses and a plurality of first segments 301 and secondsegments 302 disposed under the array 305 of lenses. Referring to FIG.3B, the first segments 301 a, 301 b, 301 c, 301 d can correspond toportions of a first image 310 (only top portion illustrated). The secondsegments 302 a, 302 b, 302 c, 302 d can correspond to portions of asecond image 320 (only top portion illustrated). The first image 310 caninclude a first icon 312 and a first background 315. The second image320 can include a second icon 322 and a second background 325. Thus,instead of switching an icon 112 on and off, the example embodimentshown in FIGS. 3A and 3B can switch between two icons 312, 322, or moreparticularly, between two images 310, 320 with each image 310, 320having an icon 312, 322 and a background 315, 325.

For example, at a first viewing angle α, the array 305 of lenses can beconfigured to allow the first image 310 for viewing without allowing thesecond image 320 for viewing. At a second viewing angle β different fromthe first viewing angle α, the array 305 of lenses can be configured toallow the second image 320 for viewing without allowing the first image310 for viewing. Referring to FIG. 3B, the first segments 301 caninclude specular reflecting features 332 and diffusing features 335.Instead of the second segments 102 only including either specularreflecting features or diffusing features 145, the second segments 302can include both specular reflecting features 342 and diffusing features345.

For the first 301 and second 302 segments, the specular reflectingfeatures 332, 342 can define either the icon 312, 322 or the background315, 325. If the specular reflecting features 332, 342 define the icon312, 322, then the diffusing features 335, 345 can define the background315, 325. On the other hand, if the diffusing features 335, 345 definethe icon 312, 322, then the specular reflecting features 332, 342 candefine the background 315, 325. In further embodiments, the specularreflecting features (e.g., the specular reflecting features 332, 342)can define the icon (e.g., the first icon 312) in one set of segments(e.g., the first segments 301) yet define the background (e.g., thesecond background 325) in the other set of segments (e.g., the secondsegments 302).

In FIG. 3A, the specular reflecting features 332 in the first segments301 define the first icon 312, and the diffusing features 335 define thefirst background 315. The specular reflecting features 342 in the secondsegments 302 define the second icon 322, and the diffusing features 345define the second background 325.

As described herein, incorporating specular reflecting features 332, 342adjacent diffusing features 335, 345 can provide the relatively highcontrast between icon 312, 322 and background 315, 325 upon tilting fromviewing angle α to viewing angle β. Advantageously, security devices inaccordance with certain embodiments can present for viewing a sharp iconthat switches rapidly to another sharp icon with little, if no,transitional state, which are difficult to reproduce. The rapidswitching from one icon to another can occur even when the icons 312,322 have different overall shapes from each other.

Similar to the disclosure herein with respect to the embodiment shown inFIGS. 1A and 1B, in certain embodiments, the outer shape 325 b of thesecond background 325, the size of the second background 325, and thediffusing features 345 of the second segments 302 can be the same ordifferent than the outer shape 315 b of the first background 315, thesize of the first background 315, and the diffusing features 335 of thefirst segments 301. In embodiments where they are the same, the viewercan see the icons 312, 322 switch from one to another against a similarbackground 315, 325 (e.g., in shape, size, and brightness) upon tiltingthe device 300 from the first viewing angle α to the second viewingangle β. Thus, in various embodiments, at the first viewing angle α, thearray 305 of lenses can present for viewing the first icon 312 and ashaped background 315. At the second viewing angle β, the array 305 oflenses can present for viewing the second icon 322 in the same shapedbackground 325. Although the array 305 of lenses switch from the firstbackground 315 to the second background 325, the viewer sees an icon 312switch to another icon 322 while the background 315 appears unchanged.

Similar to FIG. 2C, FIG. 3C schematically illustrates certain images andeffects that can be presented during viewing at an angle in the speculardirection by a security device in accordance with certain embodimentsdescribed herein. Similar to FIG. 2D, FIG. 3D schematically illustratescertain images and effects that can be presented during viewing at anangle not in the specular direction by the security device in accordancewith certain embodiments described herein. In this example, the specularreflecting features 332 define the first icon 312, and the diffusingfeatures 335 define the first background 315. The specular reflectingfeatures 342 define the second icon 322, and the diffusing features 345define the second background 325. Referring to FIG. 3C, the icons 312,322 appear very bright (e.g., high reflectance) against a matte white orgrey background 315, 325. Referring to FIG. 3D, the icons 312, 322appear dark (e.g., low reflectance) against a matte white or greybackground 315, 325. In both viewing situations, there is high contrastbetween the icons 312, 322 and the backgrounds 315, 325.

In various embodiments, as the device 300 is tilted from negativethrough the normal and to positive angles, a viewer can see an imageflip between a first dark icon 312 against a first matte white or greybackground 315 and a second dark icon 322 against a second matte whiteor grey background 325 (e.g., FIG. 3D). The icons 312, 322 and thebackgrounds 315, 325 are achromatic. As the device 300 is tilted to theangle of specular reflectance, a first shiny icon 312 against a firstmatte white or grey background 315 (e.g., FIG. 3C) can appear. Upon afurther slight tilt, the first shiny icon 312 against the first mattewhite or grey background 315 can flip to a second shiny icon 322 againsta second matte white or grey background 325 (e.g., FIG. 3C). As thedevice 300 is tilted out of the angle of specular reflectance andbeyond, the viewer can once again see an image flip between the firstdark icon 312 against the first matte white or grey background 315 andthe second dark icon 322 against the second matte white or greybackground 325 (e.g., FIG. 3D).

Although the example embodiment shown in FIGS. 3A and 3B illustrates asingle icon 312 switching to another single icon 322, in someembodiments, multiple icons can switch to other icons. In FIGS. 3A and3B, the security device 300 can include a plurality of lenses forming anarray 305 of lenses along a longitudinal axis 307.

Referring to FIG. 4A, the first segments (e.g., first segments 301 inFIGS. 3A and 3B) can correspond to portions of a first set 401 a of atleast two icons 411 a, 412 a. The second segments 302 can correspond toportions of a second set 402 a of at least two icons 421 a, 422 a. Theicons in each set 401 a, 402 a can be separated by background. At afirst viewing angle α, the array 305 can be configured to allow thefirst set 401 a of two or more icons 411 a, 412 a to be viewable, e.g.,in a row along an axis 407 perpendicular to the longitudinal axis 307 ofthe array 305 of lenses. At a second viewing angle β, different from thefirst viewing angle β, the array 305 of lenses can be configured toallow the second set 402 a of two or more icons 421 a, 422 a to beviewable, e.g., in a row along the axis 407 perpendicular to thelongitudinal axis 307 of the array 305 of lenses. In variousembodiments, one or more of the multiple icons 411 a, 412 a of the firstset 401 a can be different from a corresponding one of the multipleicons 421 a, 422 a in the second set 402 a. For example, for two icons411 a, 412 a, each icon can switch to the same or to a different icon,resulting in 4 (e.g., 2×2) different possible icon combinations. Asanother example, for two icons 411 a, 412 a, each icon has thepossibility to be in one of three states, e.g., same icon, differenticon, or no icon. In such an example, there are 9 (e.g, 3×3) differentpossible icon combinations. In the example shown in FIG. 4A, the icons411 a, 412 a at the first viewing angle α and the icons 421 a, 422 a atthe second viewing angle β are arranged in a row along the axis 407.However, other arrangements are possible.

As another example, referring to FIG. 4B, the first segments (e.g.,first segments 301 in FIGS. 3A and 3B) can correspond to portions of afirst set 401 b of at least three icons 411 b, 412 b, 413 b. The secondsegments 302 can correspond to portions of a second set 402 b of atleast three icons 421 b, 422 b, 423 b. The icons in each set 401 b, 402b can be separated by background. At a first viewing angle α, the array305 can be configured to allow the first set 401 b of three or moreicons 411 b, 412 b, 413 b to be viewable, e.g., in a row along an axis407 perpendicular to the longitudinal axis 307 of the array 305 oflenses. At a second viewing angle β, different from the first viewingangle β, the array 305 of lenses can be configured to allow the secondset 402 b of three or more icons 421 b, 422 b, 423 b to be viewable,e.g., in a row along the axis 407 perpendicular to the longitudinal axis307 of the array 305 of lenses. In various embodiments, one or more ofthe multiple icons 411 b, 412 b, 413 b of the first set 401 b can bedifferent from a corresponding one of the multiple icons 421 b, 422 b,423 b in the second set 402 b. For example, for three icons 411 b, 412b, 413 b each icon can switch to the same or to a different icon,resulting in 8 (e.g., 2×2×2) different possible icon combinations. Asanother example, for three icons 411 b, 412 b, 413 b each icon has thepossibility to be in one of three states, e.g., same icon, differenticon, or no icon. In such an example, there are 27 (e.g, 3×3×3)different possible icon combinations. In the example shown in FIG. 4B,the icons 411 b, 412 b, 413 b at the first viewing angle α and the icons421 b, 422 b, 423 b at the second viewing angle θ are arranged in a rowalong the axis 407. However, other arrangements are possible.

Furthermore, as another example, referring to FIG. 4C, the firstsegments (e.g., first segments 301 in FIGS. 3A and 3B) can correspond toportions of a first set 401 c of at least four icons 411 c, 412 c, 413c, 414 c. The second segments 302 c can correspond to portions of asecond set 402 c of at least four icons 421 c, 422 c, 423 c, 424 c. Theicons in each set 401 c, 402 c can be separated by background. At afirst viewing angle α, the array 305 can be configured to allow thefirst set 401 c of four or more icons 411 c, 412 c, 413 c, 414 c to beviewable, e.g., in a row along an axis 407 perpendicular to thelongitudinal axis 307 of the array 305 of lenses. At a second viewingangle β, different from the first viewing angle β, the array 305 oflenses can be configured to allow the second set 402 c of four or moreicons 421 c, 422 c, 423 c, 424 c to be viewable, e.g., in a row alongthe axis 407 perpendicular to the longitudinal axis 307 of the array 305of lenses. In various embodiments, one or more of the multiple icons 411c, 412 c, 413 c, 414 c of the first set 401 c can be different from acorresponding one of the multiple icons 421 c, 422 c, 423 c, 424 c inthe second set 402 c. For example, for four icons 411 c, 412 c, 413 c,414 c, each icon can switch to the same or to a different icon,resulting in 16 (e.g., 2×2×2×2) different possible icon combinations. Asanother example, for four icons 411 c, 412 c, 413 c, 414 c, each iconhas the possibility to be in one of three states, e.g., same icon,different icon, or no icon. In such an example, there are 81 (e.g,3×3×3×3) different possible icon combinations. In some examples, iconscan be spaced by other icons that turn on or off at different angles.For example, at a first viewing angle, the first and third icons 411 c,413 c can be turned on, while the second and fourth icons 412 c, 414 care turned off. At a second viewing angle, the first and third icons 411c, 413 c can be turned off, while the second and fourth icons 412 c, 414c are turned on. As another example, at a first viewing angle, the firstand fourth icons 411 c, 414 c can be turned on, while the second andthird icons 412 c, 413 c are turned off. At a second viewing angle, thefirst and fourth icons 411 c, 414 c can be turned off, while the secondand third icons 412 c, 413 c are turned on. As another example, only thefirst icon 411 c can be turned on, followed by only the second icon 412c turned on, followed by only the third icon 413 c turned on, followedby only the fourth icon 414 c turned on. In the example shown in FIG.4C, the icons 411 c, 412 c, 413 c, 414 c at the first viewing angle αand the icons 421 c, 422 c, 423 c, 424 c at the second viewing angle θare arranged in a row along the axis 407. However, other arrangementsare possible.

In certain embodiments, the device can provide a stereoscopic view or a3D effect. For example, the first and second segments can correspond toportions of a right side and left side view of an object or an icon oran icon and a background. In some such embodiments, the lenses in thearray of lenses (and the first and second segments) can have alongitudinal axis disposed in the vertical direction (e.g., cylindricallenses with curvature in the horizontal direction). When tilting thedevice about the longitudinal axis of the lenses, the array of lensescan be configured to present the right and left side views of the imagefor a stereoscopic view of the image. As disclosed herein, the first andsecond segments can include specular reflecting features and diffusingfeatures. In some embodiments, the specular reflecting features definethe icon and the diffusing features define the background. In some otherembodiments, the diffusing features define the icon and the specularreflecting features define the background. In various embodiments, thefirst and second segments can correspond to portions of at least threeimages (e.g., 3, 4, 5, 6, 7, 8, 9, etc.). An image of an icon or objectfrom a different perspective and angle can provide these multiple views.In some such embodiments, when the device is tilted about thelongitudinal axis of the lenses, the viewer can observe around the iconin the image.

For additional security, various embodiments of features describedherein can be combined together and/or with other features known in theart or yet to be developed. For example, certain embodiments can furthercomprise another optical element (e.g., a holographic element, adiffractive element, or a non-holographic and non-diffractive element).The additional optical element can be disposed under the array 105, 305of lenses (within or outside of the first 101, 301 and/or second 102,302 segments) or outside of the array 105, 305 of lenses. As anotherexample, various embodiments can include one or more micro-structurallenses (e.g., Fresnel lens or a diamond turned element). Themicro-structural lenses can be overprinted in some cases. Furthermore,as yet another example, some embodiments can include optically variableink and/or interference features in thin films.

FIG. 5A schematically illustrates certain features of an examplesecurity device 500 in accordance with certain embodiments describedherein. Like the other embodiments described herein, the security device500 can include specular reflecting features 132, 332, 342 and diffusingfeatures 135, 335, 345 under an array 105, 305 of lenses (showncollectively as 501). As shown in FIG. 5A, some embodiments can includea metallized coating 502 with a portion 503 without metallization (e.g.,either demetallized or selectively metallized) to form at least onealphanumeric character, a symbol, an image, or an object. In someinstances, the metallized coating 502 can include aluminum, silver,gold, copper, titanium, zinc, tin, or alloys thereof (e.g., bronze). Theportion 503 without metallization can be outside or within the array oflenses 501. In various embodiments, the array of lenses can also extendover the metallized region 502 and the region 503 without metallization.

In some embodiments including a metallized region 502, the device can beincorporated into a security thread laid across a whole sheet ofbanknotes. When cutting the sheets into individual banknotes, themetallized region 502 of the security thread may be at a location thatwill be cut. Cutting the banknotes along a metallized region can thuscause the banknote to be susceptible to corrosion attack. For example,oxidation can occur or a ragged edge can be created near the cut in themetallized region. To help prevent these susceptible regions, regionswithout metallization in areas of the thread to be cut and/or aprotective coating can be applied in some embodiments to help protectthe edge of the metallization. For example, FIG. 5B-1 schematicallyillustrates a top view of a security thread. The security thread 520includes a metallized area 522 (e.g., from a metallized layer on thebottom surface, but viewable from the top surface). A region withoutmetallization 524 (e.g., either by demetallization or selectivelymetallization) can be created at the area of the security thread 520where the banknote is to be cut 526. FIG. 5B-2 schematically illustratesa side view of this security thread 520 shown in FIG. 5B-1. FIG. 5B-2shows an array 521 of lenses disposed on a substrate 527. As shown inFIGS. 5B-1 and 5B-2, the metallized area 522 (e.g., an aluminum layer)on the bottom side of the substrate 527 does not extend to the edge ofthe banknote (e.g., either by demetallization or selectivemetallization) where the thread is to be cut. A protective layer 530(e.g., a protective organic coating) can also be applied on the bottomsurface covering the metallized area 522 and the unmetallized regions524 to strengthen the edge of the banknote where the metallized area 522would otherwise have been cut.

FIG. 5C schematically illustrates certain features of an examplesecurity device 550 in accordance with certain embodiments describedherein. Like the other embodiments described herein, the security devicecan include an array of lenses, and a plurality of first and secondsegments disposed under the array of lenses. The first segments cancorrespond to portions of a first icon and a first background. Thesecond segments can correspond to portions of a second icon and a secondbackground. At a first viewing angle α, the array of lenses can beconfigured to allow the first icon and the first background to beviewable without allowing the second icon to be viewable. At a secondviewing angle β different from the first viewing angle, the array oflenses can be configured to allow the second icon and the secondbackground to be viewable without allowing the first icon to beviewable. In the embodiment shown in FIG. 5C, the first segments caninclude a first surface texture 551 defining the first icon. The secondsegments can include a second surface texture 552 defining the secondicon. The second surface texture 552 can have a surface texturedifferent from the first surface texture 551. The first and secondsegments can further include a third surface texture 553 defining thefirst and second backgrounds respectfully, The third surface texture 553can be different from the first 551 and second 552 surface textures. Forexample, the first surface texture 551 can include a moth eye texture(e.g., texture producing dark reflectance). The second surface texture552 can include an interference grating. The third surface texture 553can include a diffusing texture as described herein. In some suchembodiments, the relatively high contrast between diffusing texture anda moth eye texture or an interference grating can present for viewing asharp image.

As another example, the first surface texture 551 can include a moth eyetexture, while the second surface texture 552 can include specularreflecting features 132, 332, 342 as described herein. The third surfacetexture 553 can include a diffusing texture as described herein. As yetanother example, the first surface texture 551 can include the specularreflecting features 132, 332, 342 as disclosed herein, while the secondsurface texture 552 can include an interference grating. The thirdsurface texture 553 can include a diffusing texture as described herein.In some embodiments, the first 551 and second 552 surface textures canbe in contact with each other. In additional embodiments, the first 551and second 552 surface textures might not be in contact with each other.

FIG. 6A shows the relative brightness (relative intensity units) as afunction of distance (e.g., 150 data points over 5 mm) of a line scanacross an icon in an example security device in accordance with certainembodiments described herein. The icon is represented by the number “1”.When viewing the example device at an angle in the specular direction, ashiny icon such as one having a bright aluminum color against a mattewhite or grey background (or potentially colored by tint, dye, ink,pigment, or other absorptive material) can be viewed. As shown in trace602, the relative brightness increases and decreases as the scan passesthrough the shiny icon. When viewing the example device at an angle notin the specular direction, a dark or black icon against a matte white orgrey background can be viewed. As shown in trace 604, the relativebrightness decreases and increases as the scan passes through the darkicon. The contrast between the icon and the background can becharacterized as the height of the deviation from the background. Inthis example, the contrast is similar (e.g., the brightness is almostequal to the darkness such as between 120 and 125 relative intensityunits) for both viewing conditions. In various embodiments, the contrastcan be similar for both viewing conditions by ±5%, ±7%, or ±10%.

As described herein, one way to characterize the line definition (e.g.,border) can be by the differential (e.g., derivative or slope) acrossthe boundary. For example, relatively high contrast and a sharp bordercan have a high and/or narrow differential trace, while relatively lowcontrast and not so sharp border can have a low and/or wide differentialtrace. FIGS. 6B-1, 6B-2, 6B-3, and 6B-4 show the relatively highcontrast and sharpness of the edges of the icons presented in certainembodiments of devices described herein. For example, FIGS. 6B-1 and6B-2 show relatively narrow differential traces for the line definitionof the shiny “1” icon and dark “1’ icon respectively. FIGS. 6B-3 and6B-4 show relatively narrow differential traces for the line definitionof the shiny “U” icon and dark “U’ icon respectively.

Table 1 shows the security effect from the human eye perspective of anexample security device in accordance with certain embodiments describedherein. As the example security device was tilted under an LED (with adiffuser), the presented icon was noted at each angle as well as thecontrast of it relative to the diffuse background. The icon eitherappeared shiny (aluminum color) or appeared black against a matte whitebackground. The angle of the device was determined by viewing amagnetically attached protractor having a needle pointed to the angle ofthe tilt. The results are shown schematically in FIG. 7. For example,FIG. 7 schematically illustrates the change in brightness of the twoicons switching for various angles of tilt in the example device used inTable 1. In this example, the icons switched at tilt angles less than 15degrees. The minimum tilt angle was 5 to 6 degrees with an average of 9degrees. The icon appeared shiny against a black background for most ofthe angles measured due to the diffuser at the exit of the LED.

TABLE 1 Angle Delta angle Icon Contrast −44 B Silver −33 11 A Black −276 B Black −19 8 B Silver −9 10 A Silver 3 12 B Silver 8.5 5.5 A Silver17 8.5 B Silver 27 10 A Black

FIG. 8A shows an example icon switching from one art object shown in theleft photograph to a different art object shown in the right photographin a device according to certain embodiments disclosed herein. In thisexample, the two icons are of two different rendered images (e.g., likeengravings) or art images. On the left is one image before the tilt, andthe other image appears upon tilting the device. The same bright imagesagainst a diffuse background as well as dark icons against a diffusebackground are seen as the observer tilts the device back and forthrelative to his/her view.

This example embodiment was created utilizing half-tone patterning,e.g., as shown in FIG. 8B. In various embodiments, the amount ofspecular reflecting features can be varied by half-tone patterningand/or screening in the first segment and/or the second segment tocontrol the brightness (or the darkness, e.g., greyness) of an image.For example, the brightness (or darkness, e.g. greyness) as perceived bya viewer of an area can be modulated by the ratio of specular reflectingfeatures to diffusing features. For example, the brightness (ordarkness, e.g. greyness) as perceived by a viewer of an area within asegment can be modulated by the ratio of the area (e.g., area of thefootprint) of specular reflecting features to the area (e.g., area ofthe footprint) of the diffusing features. The size, number, and/ordistribution of the specular reflecting features relative to the size,number, and/or distribution of the diffuse reflecting features in anarea within a segment can likewise be configured to provide the level ofbrightness, darkness, (e.g., greyness). As discussed above, pigment,inks, or other absorptive material can be used to provide color, inwhich case the relative areas, size, number, and/or distribution of thespecular reflecting features relative to that of the diffuse reflectingfeatures would control the perceived brightness or darkness of the hueor color. The shape of the specular reflecting features and diffusingfeatures, for example, the area (e.g., area of the footprint) may besquare, rectangular, hexagonal, circular, or a wide variety of othershapes. Similarly the specular reflecting features and diffusingfeatures may be packed together in a wide variety of arrangements, e.g.,in a square array, triangular array, hexagonally closed packed, or inother arrangements. In FIG. 8B, the black regions can represent regionsof diffusing features (or the specular reflecting features), while thewhite regions can represent the specular reflecting features (or thediffusing features). An un-aided eye typically cannot discern the imageas a half-tone image if the half-tone features are less than around 75microns. Accordingly, in various embodiments, a minimum half-tonefeature in the half-tone patterning can be less than or equal to 75microns (e.g., less than or equal to 65 microns, less than or equal to50 microns, less than or equal to 30 microns, less than or equal to 10microns, etc.) and/or be in a range from 0.05 micron to 75 microns(e.g., 0.05 micron to 65 microns, 0.05 micron to 50 microns, 0.05 micronto 30 microns, 0.05 micron to 10 microns, 1 micron to 75 microns, 1micron to 50 microns, etc.), in any range within this range, any valueswithin these ranges, or in any ranges formed by such values. FIG. 8Cschematically illustrates an example device utilizing half-tonepatterning in accordance with certain embodiments described herein. Theexample device can be configured to present images such as those in FIG.8A.

FIG. 9 schematically illustrates certain images and effects that can bepresented for viewing by a security device in accordance with certainembodiments described herein. As disclosed herein, shape and/or size ofthe first background and second background can be the same or differentfrom each other. FIG. 9 shows the first background 915 having a shape915 b different than the shape 925 b of the second background 925. Thisconcept can be extended for any number of levels of icons within icons.For example the shaped background 915, 925 can be considered in thiscase another shaped icon, albeit with the same or different surfacetexture. FIG. 9 shows an icon 912 within an icon 915 that switches to adifferent icon 922 within an icon 925.

As described herein, various embodiments can switch between anachromatic image appearing and disappearing or between a firstachromatic image to a second different achromatic image. The achromaticimage(s) can include features (e.g., specular reflecting and/ordiffusing) that provide no diffractive or interference color. As alsodescribed herein, in some embodiments, the image(s) can include colorvia a tint, ink, dye, or pigment in one or more of the portionscomprising specular reflective features, portions comprising diffusingfeatures, lenses in the lens array, and/or substrate.

In some embodiments, color can be provided in an image (e.g., in an iconor background) by one or more color generating structures, such asmicrostructure and/or nanostructure configured to provide color. Forexample, FIG. 10A schematically illustrates an example color generatingstructure including a plasmonic structure 1000. The plasmonic structure1000 can include a plurality of microfeatures and/or nanofeatures. Forsimplicity, the plasmonic structure 1000 will be described as havingnanofeatures. In various embodiments, the plasmonic structure 1000 caninclude microfeatures and/or a combination of microfeatures andnanofeatures.

With reference to FIG. 10A, the plasmonic structure 1000 can include afirst metal nanofeature 1002, a second metal nanofeature 1003, and adielectric nanofeature 1004 therebetween. The first metal nanofeature1002 and the second metal nanofeature 1003 can be made of any reflectivemetal, such as silver, aluminum, gold, copper, tin, combinationsthereof, etc. In various embodiments, the first metal nanofeature 1002and the second metal nanofeature 1003 can be made of the same reflectivemetal. The dielectric nanofeature 1004 can be made of a dielectricmaterial. In some embodiments, the dielectric material can be a UVcurable resin. Other materials are possible. As shown in FIG. 10A, thedielectric nanofeature 1004 can have a depth D, a width W, and aperiodicity (e.g., pitch) P with other dielectric nanofeatures 1004. Thefirst metal nanofeature 1002 and/or the second metal nanofeature 1003can also have a depth, a width, and a periodicity.

Without being bound by theory, in various embodiments, light having acertain wavelength can be funneled into one or more of the first metalnanofeature 1002, the second metal nanofeature 1003, and/or thedielectric nanofeature 1004 via plasmonic resonance. For example, insome embodiments, the wavelength that is funneled can be based at leastin part on one or more of the dielectric nanofeature's 1004 depth D,width W, and/or periodicity P with other dielectric nanofeatures 1004.For example, the D can be in the range of 50 nm to 300 nm, 50 nm to 275nm, 50 nm to 250 nm, 50 nm to 200 nm, 75 nm to 300 nm, 75 nm to 250 nm,75 nm to 200 nm, 100 nm to 300 nm, 100 nm to 250 nm, 100 nm to 200 nm,in any ranges formed by any of these ranges, in any ranges within theseranges, any values within these ranges, or in any ranges formed by suchvalues. As another example, the P can be in the range of 50 nm to 400nm, 50 nm to 375 nm, 50 nm to 350 nm, 50 nm to 300 nm, 75 nm to 400 nm,75 nm to 350 nm, 100 nm to 300 nm, in any ranges formed by any of theseranges, in any ranges within these ranges, any values within theseranges, or in any ranges formed by such values. As another example, theW can be in the range of 10 nm to 200 nm, 10 nm to 175 nm, 10 nm to 150nm, 10 nm to 100 nm, 20 nm to 200 nm, 20 nm to 150 nm, 20 nm to 100 nm,30 nm to 200 nm, 30 nm to 150 nm, 30 nm to 100 nm, 40 nm to 200 nm, 40nm to 150 nm, 40 nm to 100 nm, in any ranges formed by any of theseranges, in any ranges within these ranges, any values within theseranges, or in any ranges formed by such values. In certain embodiments,the D, W, and/or P can be selected to produce the desired color orcolors. In some embodiments, the wavelength that is funneled can bebased at least in part on one or more of the first 1002 or second 1003metal nanofeature's depth, width, and/or periodicity. In some examples,the plasmonic structure 1000 can include a patterned structure such thatthe patterning can produce the desired color or colors. In variousembodiments, the produced color can be independent of viewing angle.

In some embodiments, the plasmonic structure 1000 can operate as areflective plasmonic structure. Without subscribing to any scientifictheory, incident light can be reflected in some embodiments as filteredlight, e.g., after absorption of the resonance wavelength. In someembodiments, the plasmonic structure 1000 can include a reflectivenanofeature 1005 (or microfeature), for example, disposed over thedielectric nanofeature 1004. The reflective nanofeature 1005 can includea reflective metal as described for the first metal nanofeature 1002and/or the second metal nanofeature 1003. In some such examples, theplasmonic structure 1000 can be configured to reflect the filteredlight.

In some embodiments, the first metal nanofeature 1002, the second metalnanofeature 1003, and the reflective nanofeature 1005 can be provided bya unitary structure. In some such examples, the unitary structure can beprovided by a coating, e.g., a coating over and between a plurality ofdielectric nanofeatures 1004. In some instances, the coating can be aconformal coating. As another example, the unitary structure can beprovided by a monolithic block of metallic material that is formed intothe first metal nanofeature 1002, the second metal nanofeature 1003, andthe reflective nanofeature 1005. In some other embodiments, the firstmetal nanofeature 1002, the second metal nanofeature 1003, and thereflective nanofeature 1005 can be provided by separate pieces.

In some embodiments as shown in FIG. 10B, the plasmonic structure 1000can operate as a transmissive plasmonic structure. Without subscribingto any scientific theory, incident light can be reflected and/ortransmitted, e.g., after absorption of the resonance wavelength. In someembodiments, the plasmonic structure 1000 may not include the reflectivenanofeature 1005 over the dielectric nanofeature 1004. In some suchexamples, the plasmonic structure 1000 can be configured to transmitsome of the filtered light. In some of these examples, the plasmonicstructure 1000 can filter light in two directions. Some such embodimentscan function as a dichroic plasmonic structure where the reflected lightand the transmitted light may produce two different colors.

FIG. 11 schematically illustrates an example color generating structure(e.g., a microstructure and/or a nanostructure configured to providecolor) including an opal structure. In some embodiments, the opalstructure can include a reverse (or inverse) opal structure 1100 asshown in FIG. 11. For simplicity, the reverse opal structure 1100 willbe described. However, it would be appreciated that in some embodiments,the opal structure can include a positive opal structure and/or acombination of a reverse and positive opal structure. With reference toFIG. 11, the reverse opal structure 1100 can include one or moremicrosurface or nanosurface relief portions 1101. For simplicity, thereverse opal structure 1100 will be described as having microsurfacerelief. In various embodiments, the opal structure 1100 can includenanosurface relief and/or a combination of microsurface and nanosurfacerelief. The microsurface relief portion 1101 can have a depth D, a widthW, and a center-to-center distance and/or periodicity (e.g., pitch) Pwith other microsurface relief portions 1101. In some embodiments, themicrosurface relief portion 1101 can be a hemisphere (or close to ahemisphere) such that 2D is substantially equal to W. However, in someembodiments, the portion of the microsurface relief might not be ahemisphere such that 2D is greater than or less than W. For example, themicrosurface relief portions 1101 may be hemi-ellipsoidal or some othershape. Some embodiments can include a plurality of microsurface reliefportions 1101, e.g., microsurface relief portions 1101 arranged in a 2Darray. Additionally, although FIG. 11 shows a plurality of microsurfacerelief portions 1101 appearing to be without spacing in between themicrosurface relief portions 1101, various embodiments can have spacingin between the microsurface relief portions 1101 such that P is greaterthan W.

In some embodiments, the reverse opal structure 1100 can be made of adielectric material. For example, the reverse opal structure 1100 can bemade of a UV curable resin. In various embodiments, the reverse opalstructure 1100 can comprise a patterned microsurface relief.

Without being bound by theory, in some embodiments, the periodicity Pcan create a photonic bandgap, where transmission of incident lighthaving a wavelength corresponding to the photonic bandgap is forbidden.In various embodiments, the reverse opal structure 1100 can operate as areflective opal structure. For example, the reverse opal structure 1100can include an opaque reflective coating on the surface of themicrosurface relief portion 1101. Some example coatings can include anyopaque reflective metal such as aluminum, silver, gold, copper, tin,combinations thereof, etc. Other examples are possible. In some suchembodiments, the reverse opal structure 1100 can be configured toreflect the filtered light.

In some embodiments, the reverse opal structure 1100 can operate as atransmissive opal structure. For example, the reverse opal structure1100 can include a transparent coating on the surface of themicrosurface relief portion 1101. Example coatings can include adielectric material having a relatively high index of refraction, e.g.,greater than or equal to 1.8, greater than or equal to 1.9, greater thanor equal to 2.0, greater than or equal to 1.8 and less than 3.0, etc.Some such examples can include zinc sulfide, titanium dioxide, indiumtin oxide, combinations thereof, etc. Other examples are possible. Insome such embodiments, the reverse opal structure 1100 can be configuredto reflect and/or transmit the filtered light. In various embodiments,the reverse opal structure 1100 can include both reflective andtransparent coatings and/or partially reflective/partially transmissivecoatings. In some instances, the reverse opal structure 1100 can includea patterned metal coated with dielectric material

Without being bound by theory, in some embodiments, the color of thefiltered light can also be created by diffraction and/or Braggdiffraction and can also be based at least in part on one or more of themicrosurface relief portion's depth D, width W, and/or periodicity P.For example, the D can be in the range of 0.3 microns to 0.7 microns,0.3 microns to 0.65 microns, 0.35 microns to 0.7 microns, 0.35 micronsto 0.65 microns, 0.03 microns to 0.6 microns, 0.35 microns to 0.6microns, 0.4 microns to 0.6 microns, in any ranges formed by any ofthese ranges, in any ranges within these ranges, any values within theseranges, or in any ranges formed by such values. As another example, theW can be in the range of 0.5 microns to 2 microns, 0.5 microns to 1.5microns, 0.5 microns to 1 microns, in any ranges formed by any of theseranges, in any ranges within these ranges, any values within theseranges, or in any ranges formed by such values. As another example, theP can be in the range of 0.1 microns to 0.6 microns, 0.2 microns to 0.5microns, 0.25 microns to 0.45 microns, in any ranges formed by any ofthese ranges, in any ranges within these ranges, any values within theseranges, or in any ranges formed by such values. In certain embodiments,the D, W, and/or P can be selected to produce the desired color orcolors. In some examples, the opal structure 1100 can include apatterned structure such that the patterning can produce the desiredcolor or colors. In various embodiments, the produced color can bedependent on the viewing angle.

The opal structure (reverse, positive, or combination thereof) caninclude a plurality of aligned and/or repeating microsurface and/ornanosurface relief portions 1101. In some instances, for an additionalsecurity feature, the opal structure can include a misalignment and/oran irregularity to provide a forensic signature (e.g., an identifyingmark). For example, the microsurface and/or nanosurface relief portions1101 can be misaligned. As another example, the plurality of reliefportions can include a differently sized or shaped relief portion 1101,a missing relief portion 1101, and/or other defect. In some embodiments,the misalignment and/or irregularity in the opal structure itself maynot be viewable with the unaided eye, but can be viewable with anadditional aid such as a white light interferometer, an atomic forcemicroscope, a scanning electron microscope, etc. As another example, themisalignment and/or irregularity can be incorporated into a micro-image(e.g., an alphanumeric character, symbol, an art image, graphic, or anobject) such that a misalignment and/or irregularity is presented in themicro-image (e.g., a crooked line, a speck of blue in orange text,etc.). In some such embodiments, the misalignment and/or irregularity inthe micro-image may not be viewable with the unaided eye, but can beviewable with an additional aid such as a magnifying glass ormicroscope, etc. In some embodiments, the misalignment and/orirregularity in the micro-image may be viewable with the unaided/nakedeye.

Various embodiments can include one or more color generating structures(e.g., microstructure and/or nanostructure configured to provide one ormore colors such as a plasmonic structure, a reverse opal, a positiveopal, and/or combinations thereof) under an array of lenses as describedherein. For example, some embodiments including one or more colorgenerating structures can be disposed under an array of 1D lenses asdescribed herein. As another example, some embodiments including one ormore color generating structures can be disposed under an array of 2Dlenses as described herein. For example, any of the examples describedherein (e.g., FIGS. 1A to 9) can include one or more color generatingstructures to provide one or more colors. Also, any of the examplesdescribed herein (e.g., FIGS. 1A to 9) can substitute one or morefeatures (e.g., specular reflecting and/or diffusing features) with oneor more color generating structures. One or more color generatingstructures can be added such that color is above eye resolution (e.g.,at least 100 microns or more) and viewable with the naked eye. Some suchembodiments can also provide a security feature of an identifying mark(e.g., a colored dot, a colored mark, color in at least a portion of agraphic, color in at least a portion of text, etc.). Alternatively, asan additional security feature, one or more color generating structurescan be added such that the color is below eye resolution (e.g., lessthan 100 microns) and not viewable with the naked eye, but viewable withthe aid of, e.g., a magnifying glass or microscope.

As an example, with reference to FIGS. 1A and 1B, one or more colorgenerating structures (e.g., 1000 or 1100 shown in FIGS. 10A, 10B, and11) can be incorporated into a first segment 101 a, 101 b, 101 c, and/or101 d to provide a color for the view 110 of the icon 112 (e.g., to atleast a portion of the icon 112 and/or background 115). Additionally oralternatively, one or more color generating structures can beincorporated into a second segment 102 a, 102 b, 102 c, and/or 102 d toprovide color to the view 120 without the icon 112. One or more colorgenerating structures can be incorporated into the specular reflectingfeatures 132 and/or diffusing features 135 of the first segments 101and/or into the diffusing features 145 of the second segments 102. Insome embodiments, one or more color generating structures can besubstituted for the specular reflecting features 132 and/or thediffusing features 135 in the first segments 101 and/or for thediffusing features 145 of the second segments 102.

As another example, with reference to FIGS. 3A and 3B, one or more colorgenerating structures can be incorporated into a first segment 301 a,301 b, 301 c, and/or 301 d to provide a color for the first image 310(e.g., to at least a portion of the icon 312 and/or background 315).Additionally or alternatively, one or more color generating structurescan be incorporated into a second segment 302 a, 302 b, 302 c, and/or302 d to provide color to the second image 320 (e.g., to at least aportion of the icon 322 and/or background 325). One or more colorgenerating structures can be incorporated into the specular reflectingfeatures 332 and/or diffusing features 335 of the first segments 301and/or into the specular reflecting features 342 and/or diffusingfeatures 345 of the second segments 302. In some embodiments, one ormore color generating structures can be substituted for the specularreflecting features 332 and/or the diffusing features 335 in the firstsegments 301 and/or for the specular reflecting features 342 and/ordiffusing features 345 of the second segments 302.

As another example, with reference to FIG. 5C, one or more colorgenerating structures can be incorporated into or substituted for thefirst surface texture 551, the second surface texture 552, and/or thethird surface texture 553 to provide a color to at least a portion ofthe icon and/or background of the security device 550.

As another example, with reference to FIG. 8A, one or more colorgenerating structures can be incorporated into one or more engravinglike images. One or more color generating structures can be incorporatedinto a region disposed under the array of lenses. For example, whenincorporated into a region disposed under the array of lenses, color canbe incorporated into at least a part of one of the switching icons orbackgrounds. With reference to FIGS. 8B and 8C, one or more colorgenerating structures can be incorporated into or substituted for someor all of the half-tone features (e.g., specular reflecting and/ordiffuse features). In some embodiments, one or more color generatingstructures can be incorporated into a region other than those disposedunder the lenses. For example, when incorporated into a region otherthan those disposed under the lenses, color can be incorporated outsideof the switching icons or backgrounds.

In various embodiments, achromatic images (e.g., black, white, greys,etc.) can be provided by specular reflecting and diffusing features. Insome embodiments, one or more color generating structures can beconfigured to provide different colors in the image(s) viewed by theviewer. For example, the color generating structures can provide theprimary colors and/or secondary colors (e.g., red, green, blue or cyan,yellow, and magenta). In some embodiments, the different colors maycombine to produce a different color or a single color as perceived bythe naked eye. For example, the primary colors may in some instancescombine to form secondary colors. The primary colors may in someinstances also combine to form an achromatic appearance. For example,red, green, and blue or cyan, yellow, and magenta may combine to form anachromatic white appearance. By incorporation of color generatingstructures with specular reflecting and diffusing features, a sharp fullcolor image and/or a natural tone image can be presented. Someembodiments can be configured to provide the true color of an object.For example, some embodiments can be configured to provide a renditionof an object's natural color, e.g., through an icon or image. In someinstances, the icon or image can include a range of hues, such as morethan 5 hues, more than 10 hues, more than 15 hues, more than 20 hues, orany ranges formed by such values, etc.

FIG. 12 schematically illustrates an example method of forming variouscolor generating structures described herein. The method 1200 can besimilar to and/or compatible with the embossing method used to formvarious features (e.g., diffusing and/or specular reflecting features)as described herein. For example, the method 1200 can include forming anembossing tool 1201 such as one comprising a metal 1202 such as steel oraluminum. A master shim 1203 can be formed using an electron beam,lithographic technique, or etching. Daughter shims can be created fromthe master shim 1203. In some embodiments, the master shim 1203 can beformed in nickel, which can be attached to the metal 1202. Since themethod 1200 can be similar to and/or compatible with the embossingmethod used to form various features (e.g., diffusing and/or specularreflecting features) described herein, FIG. 12 illustrates variousfeatures (e.g., diffusing features 1210 a, 1210 b and/or specularreflecting features 1211 a, 1211 b) and color generating structures 1212(e.g., a plasmonic structure, a positive opal structure, and/or areverse opal structure) that can be formed into the master shim 1203.Advantageously, one or more color generating structures can be formedsimultaneously with one or more other color generating structures and/orone or more other features (e.g., diffusing and/or specular reflectingfeatures) described herein. In some embodiments, one or more colorgenerating structures can be formed sequentially (e.g., before or after)with one or more other color generating structures and/or one or moreother features. Some embodiments may form only one of the colorgenerating structures, while other embodiments may form more than one orall of the shown features and/or color generating structures.

As shown in FIG. 12, a substrate or carrier 1250 can be provided. Thesubstrate 1250 can be embossed or can provide support for a layer ofmaterial 1260 which can be embossed by the embossing tool 1201 to formone or more of the actual color generating structures 1262. In someinstances, heat embossing can be used to emboss a heat embossablepolymer (e.g., polyvinyl chloride) substrate 1250 or a heat embossablepolymer 1260 disposed on the substrate 1250. In some embodiments, thesubstrate 1250 or a layer of material 1260 can comprise a UV curableresin. In some such embodiments, UV light can be applied during theembossing operation to cure the resin. In some embodiments, thethickness of the UV cured resin 1260 disposed on a substrate can be in arange from 1 to 15 microns, 1 to 12.5 microns, 1 to 10 microns, 2 to 15microns, 2 to 12.5 microns, 2 to 10 microns, 1 to 7 microns, 2 to 7microns, 2 to 5 microns, in any ranges within these ranges, in anyranges formed by any of these ranges, any values within any of theseranges, in any ranges formed by such values, etc.

The substrate 1250 can be similar to the substrate described herein(e.g., substrate 150 in FIG. 1A). For example, the substrate 1250 caninclude a polymer substrate such as polyethylene terephthalate (PET) ororiented polypropylene (OPP), etc. The substrate 1250 can have athickness that can be in the range from 10 microns to 300 microns, from10 microns, to 250 microns, from 10 microns to 200 microns, from 10microns to 150 microns, from 10 microns to 100 microns, from 10 micronsto 20 microns, in any ranges formed by any of these ranges, in anyranges within these ranges, any values within these ranges (e.g., 12.5microns, 25 microns, 37.5 microns, 40 microns, 45 microns, 50 microns,80 microns, 100 microns, etc.), or in any ranges formed by such values.

Similar to FIG. 1A, the array of lenses (not shown), such as the 1D lensarray in FIG. 1C-1 or the 2D lens array in FIG. 1C-2, can be disposed ona first side 1251 of a substrate 1250. The array of lenses can bedisposed on a first side 1251 of the substrate 1250 before one or morecolor generating structures 1262 are formed in the layer of material1260. For example, the lenses can be disposed on a first side 1251 ofthe substrate 1250 before forming the color generating structure 1262.In some embodiments, the array of lenses can be disposed on a first side1251 of the substrate 1250 after one or more color generating structures1262 are formed in the layer of material 1260. In FIG. 12, the layer ofmaterial 1260 is disposed on a second side 1252 of the substrate 1250opposite the first side 1251. In some such embodiments, the array oflenses can be disposed on the first side 1251 or the second side 1252 ofthe substrate after one or more of the actual color generatingstructures are formed.

After the layer of material 1260 is embossed, for a reflective reverseopal, the material 1260 can be coated with a coating 1265 comprising areflective metal (e.g., coated with an opaque reflective metal such asaluminum, silver, gold, tin, etc.), while for a transmissive reverseopal, the material 1260 can be coated with a coating 1265 comprising atransparent (or at least partially transmissive) dielectric materialhaving a relative high index of refraction as described herein (e.g.,zinc sulfide, titanium dioxide, indium tin oxide, etc.). For areflective plasmonic structure, the material 1260 can be coated with acoating 1265 comprising a reflective metal (e.g., coated with an opaquereflective metal such as silver, gold, aluminum, copper, tin, etc.). Invarious embodiments, coating the embossed layer can comprise vacuum orevaporation coating. In some instances, since metal can be susceptibleto corrosion, the coating 1265 comprising a reflective metal can beprovided with a protective coating 1266 (e.g., a layer of dielectricmaterial or other metal such as aluminum). In a transmissive plasmonicstructure, any deposited reflective layer between the metal layers canbe removed. In some such embodiments, some of the deposited metal may belift-off or ion scrubbed at an angle. As shown in FIG. 12, the colorgenerating structure 1262 (e.g., to reflect colored light) can beincorporated with one or more diffusing features 1271 (e.g., to reflectdiffuse light) and/or one or more specular reflecting features 1272(e.g., to reflect specular light)

FIG. 13A schematically illustrates an example device in accordance withcertain embodiments described herein. The device 1300 can include anarray 1305 of lenses as described herein. For example, the array oflenses can include a UV cured resin in some embodiments. The array 1305of lenses can be a 1D lens array or a 2D array of lenses as describedherein. As described herein, each lens can have a diameter (or W_(L)along the x-axis for a lenticular lens array) from 5 microns to 200microns (such as from 10 microns to 150 microns, from 15 microns 100microns, etc.). The dimensions can depend on the application of use. Forexample, for a security device on currency, each lens can have adiameter from 5 microns to 20 microns (e.g., 5 microns, 10 microns, 15microns, etc.).

As also described herein, the lenses can be disposed on a first side1351 of a substrate 1350. In some embodiments, the thickness of thesubstrate 1350 can be based at least on part on the lens diameter in thearray of lenses. For example, in some instances, a lens having adiameter of 15 microns can be disposed on a substrate having a thicknessof 15 micron (e.g., so the image plane can be in focus). Likewise, alens having a diameter of 80 microns can be disposed on a substratehaving a thickness of 80 microns. One or more color generatingstructures 1362 (such as a reverse opal structure 1362 a, a positiveopal structure 1362 b, or a combination thereof) can be disposed on asecond side 1352 of the substrate 1350. For example, the one or morecolor generating structures 1362 can be formed in the UV curable resin1360. In various embodiments, one or more color generating structures1362 can include a reverse opal structure 1362 a or a positive opalsurface 1362 b. As described herein, some embodiments of the opalstructure 1362 can include a coating (e.g., reflective, transparent, orpartially reflective/partially transmissive). As also described herein,various embodiments can include one or more color generating structures1362 incorporated with one or more diffusing features 1371 and/or one ormore specular reflecting features 1372. As shown in FIG. 13B, one ormore color generating structures 1362 can include a plasmonic structure1362 c. As described herein, the plasmonic structure 1362 c can besurface coated with an opaque reflective material 1365 such as silver,followed by a protective coating of a dielectric material (e.g., silicondioxide) or aluminum. FIGS. 13A and 13B are not drawn to scale. Forexample, in many embodiments, the size of the opal structure 1362 a or1362 b and/or of the plasmonic structure 1362 c can be much smaller thanthe size of the lenses 1305.

In various embodiments, after the device is formed, various embodimentscan be incorporated into a banknote as described herein. The securitydevice can be configured to provide authenticity verification on an itemof security (e.g., currency, a credit card, a debit card, a passport, adriver's license, an identification card, a document, a tamper evidentcontainer or packaging, or a bottle of pharmaceuticals). The securitydevice can be a security thread, a hot stamp feature, an embeddedfeature, a windowed feature, or a laminated feature.

In some embodiments, one or more colors produced by a corresponding lensin the array of lenses can be resolved by an unaided eye. However, foradded security, in some embodiments, at least one color can be added ata covert level. For example, one or more color generating structures canbe added such that the color is below eye resolution (e.g., less than100 microns) and not viewable without aid of a magnifying glass or amicroscope. As another example, one or more color generating structurescan be added such that the colored symbol (e.g., text, number, graphic,etc.) is not resolvable without an additional aid.

As described herein, a 2D lens array as shown in FIG. 1C-2 can beincorporated in various embodiments described herein to presentimages/icons with or without color. FIG. 14A schematically illustratesan isometric view of an example security device 1040 including a 2D lensarray 1025 comprising lens elements L₁, L₂, L₃, L₄, L₅ and L₆ disposedover a plurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ having opticalfeatures as described herein. The device 1040 can be configured topresent different distinct images/icons (e.g., a liberty bell and anumber 100) when viewed from different directions. For example, asdiscussed above, at a first viewing angle, the device 1040 can presentan icon for viewing and at a second viewing angle the device 1040 doesnot present the icon for viewing. In various embodiments discussedherein, the features included in each of the plurality of portions P₁,P₂, P₃, P₄, P₅ and P₆ can be configured to produce halftone images. Asdiscussed herein, in some embodiments, each of the plurality of portionsP₁, P₂, P₃, P₄, P₅ and P₆ can comprise a plurality of features that areconfigured to produce a plurality of distinct images/icons. For example,each of the plurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ can comprisea first set of features that are configured to produce a firstimage/icon and a second set of features that are configured to produce asecond image/icon distinct from the first image/icon. As anotherexample, the plurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ cancomprise specular reflection features and diffusing features. Thespecular reflecting features can define one of the icon or thebackground. The diffusing features can define the background when thespecular reflecting features define the icon. The diffusing features candefine the icon when the specular reflecting features define thebackground. In some embodiments, each of the plurality of portions P₁,P₂, P₃, P₄, P₅ and P₆ is configured to produce a replica of the distinctimages/icons individually. In such embodiments, the 2D lens array can beconfigured to produce distinct image/icons based on the distinctimages/icons produced by each of the plurality of portions P₁, P₂, P₃,P₄, P₅ and P₆ individually. For example, each lens element of the 2Dlens array can be configured to bring into focus different aspects ofthe distinct image/icons produced by the respective portion over whichthat lens element is disposed. In this manner a magnified version of thedistinct images/icons can be produced using the lens array. In variousembodiments, any of or any combination of the size and shape of theportions P₁, P₂, P₃, P₄, P₅ and P₆ and/or the location of the icons inthe portions can be the same. In some embodiments, for example, theplurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ can be replicas of eachother.

In FIG. 14A, the plurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ aredepicted as having approximately the same size. However, in variousembodiments, the portions P₁, P₂, P₃, P₄, P₅ and P₆ need not have thesame size and/or shape. The portions P₁, P₂, P₃, P₄, P₅ and P₆ need notbe ordered or regularly arranged identically sized rows and columns.Irrespective of whether the size and the shape of each of the pluralityof portions P₁, P₂, P₃, P₄, P₅ and P₆ are the same, the differentportions P₁, P₂, P₃, P₄, P₅ and P₆ can be configured to produce the sameset of images/icons.

The size of each lens element of the 2D lens array 1025 can be matchedto the size of the portion over which it is disposed such that each ofthe plurality of portions has a corresponding lens element disposed overit. In such embodiments, there is a one-to-one correspondence betweenthe number of lens elements of the 2D lens array 1025 and the number ofthe portions. The curvature of each lens element of the 2D lens arraycan be configured to produce different optical effects and/or providedifferent amounts of magnification. Although, in FIG. 14A, the size ofthe individual lens elements of the 2D lens array is depicted as havingapproximately the same size, in other embodiments, the size of theindividual lens elements of the 2D lens array can vary. In FIG. 14A, theindividual lens elements of the 2D lens array are depicted as sphericallens elements that are in contact with the neighboring lens elementssuch that the distance between the centers of neighboring lens elements(also referred to as for example pitch) is equal to the diameter of thespherical lens element. However, in other embodiments, each lens elementof the 2D lens array can be spaced apart from a neighboring lens elementby a gap such that the distance between the centers of neighboring lenselements is greater than the diameter of the lens element. In variousembodiments, the 2D lens array can be a regular array in which thedistance between the centers of neighboring lens elements is constantacross the array. However in other embodiments, the distance between thecenters of neighboring lens elements can vary across the lens array.

The lens elements of the 2D lens array 1025 can be aligned with respectto the plurality of portions P₁, P₂, P₃, P₄, P₅ and P₆ such that eachlens element of the 2D lens array is registered with a respectiveportion. For example, the center of each lens element of the 2D lensarray 1025 can coincide with the center of a respective portion overwhich it is disposed. FIG. 14B illustrates a top view of an examplesecurity device including a 2D lens array 1025 having lens elements 1025a, 1025 b, 1025 c, 1025 d, 1025 e, 1025 f, 1025 g, 1025 h and 1025 ithat are registered with a portion P₁, P₂, P₃, P₄, P₅, P₆, P₇, P₈, andP₉ respectively such that the center of each lens element 1025 a, 1025b, 1025 c, 1025 d, 1025 e, 1025 f, 1025 g, 1025 h and 1025 i coincideswith the center of the respective portion P₁, P₂, P₃, P₄, P₅, P₆, P₇,P₈, and P₉. In the device illustrated in FIG. 14B, each portion P₁, P₂,P₃, P₄, P₅, P₆, P₇, P₈, and P₉ has optical features that are configuredto produce two distinct images/icons (e.g., a bell and the number 100).The arrangement of features that are configured to produce two distinctimages/icons (e.g., a bell and the number 100) is the same in each ofthe plurality of portions P₁, P₂, P₃, P₄, P₅, P₆, P₇, P₈, and P₉ suchthat similar regions of the lens elements 1025 a, 1025 b, 1025 c, 1025d, 1025 e, 1025 f, 1025 g, 1025 h and 1025 i are disposed over similarregions of the two distinct images/icons and/or the icons in theplurality of portions P₁, P₂, P₃, P₄, P₅, P₆, P₇, P₈, and P₉ aredisposed under similar regions of the lens.

However, in various embodiments, lens elements need not be registeredwith respect to the plurality of portions. For example, as shown in FIG.14C, the centers of the lens elements can be laterally shifted withrespect to the centers of the corresponding portions. In suchembodiments, the icons may appear to move when the device is tilted suchthat it is viewed from different directions. Although, the centers ofthe lens elements in FIG. 14C are depicted as being shifted laterallyalong the horizontal direction, in other embodiments, the centers of thelens elements can be shifted laterally along the vertical direction.

In FIG. 14D, the features in each of the plurality of portions P₁, P₂,P₃, P₄, P₅, P₆, P₇, P₈, and P₉ that are configured to produce twodistinct images/icons (e.g., a bell and the number 100) are arrangedsuch that the two distinct images/icons are produced in differentspatial regions in each of the plurality of portions P₁, P₂, P₃, P₄, P₅,P₆, P₇, P₈, and P₉. Thus, although the individual lens elements of the2D lens array are registered with a corresponding portion, the icons ofthe different portions P₁, P₂, P₃, P₄, P₅, P₆, P₇, P₈, and P₉ are not inthe same position with respect to the center of the lens. Without anyloss of generality, the plurality of portions P₁, P₂, P₃, P₄, P₅, P₆,P₇, P₈, and P₉ can be considered to form a 2D array of images thatextends along horizontal and vertical directions. As discussed herein,the array of images can be a regular array having a period (referred toherein as an image period) corresponding to the distance betweenconsecutive images. The 2D array of lenses can also extend alonghorizontal and vertical directions. In various embodiments, the lensperiod of the 2D lens array corresponding to the distance betweenconsecutive lens elements can be equal to the image period (e.g., asshown in FIG. 14B), greater than the image period or lesser than theimage period. When the lens period is greater than the image period, theimage/icon can appear beyond the image plane. When the lens period islesser than the image period, the image/icon can appear in front of theimage plane. In various embodiments, the horizontal and verticaldirections of the lens array can be aligned with the horizontal andvertical directions of the image array (as depicted in FIG. 14B) suchthat each lens element of the 2D lens array is registered (or aligned)with each element of the image array. However, in some otherembodiments, the horizontal and vertical directions along which the lensarray extends can be rotated with respect to the horizontal and verticaldirections along which the image array extends such that the lens arrayis rotated with respect to the image array as depicted in FIG. 14E. Forexample, the lens array can be rotated by an amount less than or equalto 15 degrees with respect to the image array. By rotating the lensarray with respect to the image array, the image/icon can be configuredto move in a perpendicular direction relative to the tilt direction withrespect to the observer as the viewing angle is changed. In suchembodiments, the lens period can be considered to be rotated withrespect to the image period. A similar effect can be obtained byrotating the horizontal and vertical directions along which the imagearray extends with respect to the horizontal and vertical directionsalong which the lens array extends as shown in FIG. 14F.

The 2D lens array disposed over a 2D image array can produce manydifferent optical effects. For example, the different images/icons canappear to move laterally as the optical device is tilted. As anotherexample, each of the plurality of portions can be configured to producea first version of an image/icon having a first size and a secondversion of the image/icon having a second size. As the optical device istilted, the image/icon can appear to change size without changing theirshape. The different images/icons can appear to form puzzle pieces thatintersect and/or move away from each other as the optical device istilted. The different images/icons can appear to change optical densityas the optical device is tilted. In some embodiments, each of theplurality of portions can be configured to produce a first version of animage/icon that is reflective (such that it appears bright) and a secondversion of the image/icon that is diffusive. As the optical device istilted, the image/icon can appear to change from a reflective state to adiffusive state or vice-versa while maintaining the same shape. In someembodiments, each of the plurality of portions can be configured toproduce a first version of an image/icon having a first orientation anda second version of the image/icon having a second orientation. Theorientation of the image/icon can appear to change as the device istilted. The different images/icons may appear to come closer together ormove away from each other as the optical device is tilted. The differentimages/icons may appear to move in opposite directions laterally as theoptical device is tilted. The different images/icons may appear tochange from one symbol to another, from one number to another, from onegeometric figure to another, from one logo to another, or from onepictorial representation to another as the optical device is tilted.

FIG. 14G illustrates a top view of security device comprising a lensarray disposed over an image array. The image array includes portionscomprising optical features that are configured to produce distincticons (e.g., a bell and a text 100). The features of the image arraythat produce the first icon (e.g., a bell) are rotated along a firstdirection (e.g., counter clock-wise) with respect to the centers of thelenses of the lens array and the features of the image array thatproduce the second icon (e.g., text 100) are rotated along a secondopposite direction (e.g., clock-wise) with respect to the centers of thelenses of the lens array. When the device is tilted then the first icon(e.g., a bell) and the second icon (e.g., text 100) can appear to movein different directions.

FIG. 14H illustrates a top view of security device comprising a lensarray disposed over an image array. The image array includes portionscomprising optical features that are configured to produce distincticons (e.g., a bell and a text 100). The features of the image arraythat produce the first icon (e.g., a bell) are disposed such that theycoincide with respect to the centers of the lenses of the lens array.Accordingly, the pitch of the first icons in the image (or the distancebetween adjacent first icons) is substantially equal to the pitch of thelens array. The pitch of the second icons in the image array can bedifferent from the pitch of the lens array. For example, the pitch ofthe second icons can be between about 1%-20% greater than or lesser thanthe pitch of the lens array. When the device is tilted then the secondicon (e.g., text 100) can appear to move away from or closer to thefirst icon. Many such optical effects can be created by varying theregistration of the image array and/or icons of the image array withrespect to the centers of the lenses in the lens array. For example, insome embodiments, some of the images/icons produced by the features ofthe plurality of portions can appear to be at the surface of the devicewhile some other images/icons produced by the features of the pluralityof portions can appear to float above or below the surface of thedevice.

Various embodiments of the present invention have been described herein.Although this invention has been described with reference to thesespecific embodiments, the descriptions are intended to be illustrativeof the invention and are not intended to be limiting. Variousmodifications and applications may occur to those skilled in the artwithout departing from the true spirit and scope of the invention.

What is claimed is:
 1. A security device that is achromatic comprising:an array of lenses; and a plurality of first and second segmentsdisposed under the array of lenses, the first segments corresponding toportions of a first icon and a first background, and the second segmentscorresponding to portions of a second icon and a second background,wherein at a first viewing angle, the array of lenses presents forviewing the first icon and the first background without presenting thesecond icon for viewing, and at a second viewing angle different fromthe first viewing angle, the array of lenses presents for viewing thesecond icon and the second background without presenting the first iconfor viewing, wherein individual ones of the first and second segmentscomprise specular reflecting features and diffusing features, whereinfor the first and second segments, the specular reflecting featuresdefine the first and second icons, and the diffusing features define thefirst and second backgrounds, or the diffusing features define the firstand second icons, and the specular reflecting features define the firstand second backgrounds, wherein upon viewing at an angle in the speculardirection, the first and second icons appear specularly bright and thefirst and second backgrounds appear matte white or grey when thespecular reflecting features define the first and second icons and thediffusing features define the first and second backgrounds, or the firstand second icons appear matte white or grey and the first and secondbackgrounds appear specularly bright when the specular reflectingfeatures define the first and second backgrounds and the diffusingfeatures define the first and second icons, wherein upon viewing at anangle not in the specular direction, the first and second icons appeardark relative to the first and second backgrounds, and the first andsecond backgrounds appear matte white or grey when the specularreflecting features define the first and second icons and the diffusingfeatures define the first and second backgrounds, or the first andsecond icons appear matte white or grey, and the first and secondbackgrounds appear dark relative to the first and second icons when thespecular reflecting features define the first and second backgrounds andthe diffusing features define the first and second icons.
 2. Thesecurity device of claim 1, wherein for the first and second segments,the specular reflecting features define the first and second icons andthe diffusing features define the first and second backgrounds.
 3. Thesecurity device of claim 1, wherein the first and second backgrounds arein the form of at least one alphanumeric character, a symbol, an artimage, graphic, or an object.
 4. The security device of claim 1, whereinthe first and second backgrounds further comprise a covert feature. 5.The security device of claim 4, wherein the covert feature comprises afluorescent material or an up-converting pigment.
 6. The security deviceof claim 1, wherein the array of lenses comprises a 1D lenticular lensarray.
 7. The security device of claim 1, wherein the array of lensescomprises a 2D array of lenses.
 8. The security device of claim 1,wherein the first icon flips to the second icon with no observabletransition upon a change from the first viewing angle to the secondviewing angle.
 9. The security device of claim 1, wherein the contrastpercentage between the first icon and the first background or betweenthe second icon and the second background is from 25% to 90% whenviewing at an angle in the specular direction, or from 25% to 90% whenviewing at an angle not in the specular direction.
 10. The securitydevice of claim 1, wherein for the first or second segments, thediffusing features provide Lambertian reflectance.
 11. The securitydevice of claim 1, wherein for the first or second segments, thediffusing features have an elliptical output.
 12. The security device ofclaim 1, wherein the device comprises a kinoform diffuser providing thediffusing features.
 13. The security device of claim 1, wherein for thefirst or second segments, the diffusing features comprise a brightnessin a range from 85 to 100 and a whiteness index in a range from 85 to100.
 14. The security device of claim 1, wherein for the first or secondsegments, the diffusing features comprise TiO₂ particles.
 15. Thesecurity device of claim 1, wherein for the first or second segments,the specular reflecting features and the diffusing features provide nodiffractive or interference color.
 16. The security device of claim 1,wherein the first or second icon comprises at least one alphanumericcharacter, a symbol, an art image, graphic, or an object.
 17. Thesecurity device of claim 1, further comprising a substrate having afirst side and a second side opposite the first side, wherein the arrayof lenses is disposed on the first side of the substrate, and whereinthe specular reflecting features and diffusing features are disposed onthe second side of the substrate.
 18. The security device of claim 1,wherein the security device is configured to provide authenticityverification on an item for security.
 19. The security device of claim18, wherein the item is a credit card, a debit card, currency, apassport, a driver's license, an identification card, a document, aticket, a tamper evident container or packaging, or a bottle ofpharmaceuticals.
 20. The security device of claim 1, wherein thesecurity device is a security thread, a hot stamp feature, an embeddedfeature, a windowed feature, or a laminated feature.
 21. The securitydevice of claim 1, wherein the diffusing features are viewed intransmission.
 22. The security device of claim 21, wherein for the firstor second segments, the diffusing features are coated with a transparenthigh index material.
 23. The security device of claim 21, wherein forthe first or second segments, the diffusing features are coated withZnS.
 24. The security device of claim 1, wherein the first segmentcomprises half tone.
 25. The security device of claim 24, wherein thesecond segment comprises half tone.
 26. The security device of claim 1,wherein the specular reflecting features and the diffusing features havesizes and are distributed within said first or second segment to providehalf tone imagery for producing said first or second icon.
 27. Thesecurity device of claim 1, wherein the specular reflecting features andthe diffusing features are included in said first or second segment inan amount and distribution to provide half tone imagery for producingsaid first or second icon.
 28. The security device of claim 1, whereinthe first or second segment includes specular reflecting features thatprovide half tone, wherein individual specular reflecting featurescannot be resolved in images of the specular reflecting featuresproduced by a corresponding lens in the array of lenses by the unaidedeye.
 29. The security device of claim 1, wherein the shape of the firstor second icon is invariant as the light source changes position. 30.The security device of claim 1, wherein the first or second segmentcomprises a micro-image having a height smaller than a width of thefirst or second segment.
 31. The security device of claim 30, whereinthe micro-image is at least one alphanumeric character, symbol, an artimage, graphic, or an object.
 32. The security device of claim 1,wherein the diffusing features are viewed in reflection.
 33. Thesecurity device of claim 1, wherein for the first and second segments,the diffusing features define the first and second icons and thespecular reflecting features define the first and second backgrounds.34. The security device of claim 1, wherein the second background at thesecond viewing angle appears the same in outer shape, size, andbrightness as the first background at the first viewing angle.
 35. Thesecurity device of claim 1, wherein upon viewing at an angle not in thespecular direction, the first and second icons appear black and thefirst and second backgrounds appear matte white or grey when thespecular reflecting features define the first and second icons and thediffusing features define the first and second backgrounds, or the firstand second icons appear matte white or grey, and the first and secondbackgrounds appear black when the specular reflecting features definethe first and second backgrounds and the diffusing features define thefirst and second icons.